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kernel/rcutree_plugin.h
68.1 KB
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/* * Read-Copy Update mechanism for mutual exclusion (tree-based version) * Internal non-public definitions that provide either classic |
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* or preemptible semantics. |
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* * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * * Copyright Red Hat, 2009 * Copyright IBM Corporation, 2009 * * Author: Ingo Molnar <mingo@elte.hu> * Paul E. McKenney <paulmck@linux.vnet.ibm.com> */ |
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#include <linux/delay.h> |
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#include <linux/gfp.h> |
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#include <linux/oom.h> |
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#include <linux/smpboot.h> |
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#include <linux/tick.h> |
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|
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#define RCU_KTHREAD_PRIO 1 #ifdef CONFIG_RCU_BOOST #define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO #else #define RCU_BOOST_PRIO RCU_KTHREAD_PRIO #endif |
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#ifdef CONFIG_RCU_NOCB_CPU static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */ static bool have_rcu_nocb_mask; /* Was rcu_nocb_mask allocated? */ |
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static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */ |
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static char __initdata nocb_buf[NR_CPUS * 5]; #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ |
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/* * Check the RCU kernel configuration parameters and print informative * messages about anything out of the ordinary. If you like #ifdef, you * will love this function. */ static void __init rcu_bootup_announce_oddness(void) { #ifdef CONFIG_RCU_TRACE printk(KERN_INFO "\tRCU debugfs-based tracing is enabled. "); #endif #if (defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 64) || (!defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 32) printk(KERN_INFO "\tCONFIG_RCU_FANOUT set to non-default value of %d ", CONFIG_RCU_FANOUT); #endif #ifdef CONFIG_RCU_FANOUT_EXACT printk(KERN_INFO "\tHierarchical RCU autobalancing is disabled. "); #endif #ifdef CONFIG_RCU_FAST_NO_HZ printk(KERN_INFO "\tRCU dyntick-idle grace-period acceleration is enabled. "); #endif #ifdef CONFIG_PROVE_RCU printk(KERN_INFO "\tRCU lockdep checking is enabled. "); #endif #ifdef CONFIG_RCU_TORTURE_TEST_RUNNABLE printk(KERN_INFO "\tRCU torture testing starts during boot. "); #endif |
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#if defined(CONFIG_TREE_PREEMPT_RCU) && !defined(CONFIG_RCU_CPU_STALL_VERBOSE) |
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printk(KERN_INFO "\tDump stacks of tasks blocking RCU-preempt GP. "); #endif #if defined(CONFIG_RCU_CPU_STALL_INFO) printk(KERN_INFO "\tAdditional per-CPU info printed with stalls. "); |
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#endif #if NUM_RCU_LVL_4 != 0 |
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printk(KERN_INFO "\tFour-level hierarchy is enabled. "); |
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#endif |
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if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF) printk(KERN_INFO "\tExperimental boot-time adjustment of leaf fanout to %d. ", rcu_fanout_leaf); |
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if (nr_cpu_ids != NR_CPUS) printk(KERN_INFO "\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d. ", NR_CPUS, nr_cpu_ids); |
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#ifdef CONFIG_RCU_NOCB_CPU |
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#ifndef CONFIG_RCU_NOCB_CPU_NONE if (!have_rcu_nocb_mask) { |
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zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL); |
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have_rcu_nocb_mask = true; } #ifdef CONFIG_RCU_NOCB_CPU_ZERO pr_info("\tExperimental no-CBs CPU 0 "); cpumask_set_cpu(0, rcu_nocb_mask); #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */ #ifdef CONFIG_RCU_NOCB_CPU_ALL pr_info("\tExperimental no-CBs for all CPUs "); cpumask_setall(rcu_nocb_mask); #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */ #endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */ |
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if (have_rcu_nocb_mask) { |
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cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask); pr_info("\tExperimental no-CBs CPUs: %s. ", nocb_buf); if (rcu_nocb_poll) pr_info("\tExperimental polled no-CBs CPUs. "); } #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ |
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} |
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#ifdef CONFIG_TREE_PREEMPT_RCU |
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struct rcu_state rcu_preempt_state = |
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RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu); |
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DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data); |
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static struct rcu_state *rcu_state = &rcu_preempt_state; |
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|
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static int rcu_preempted_readers_exp(struct rcu_node *rnp); |
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/* * Tell them what RCU they are running. */ |
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static void __init rcu_bootup_announce(void) |
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{ |
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printk(KERN_INFO "Preemptible hierarchical RCU implementation. "); |
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rcu_bootup_announce_oddness(); |
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} /* * Return the number of RCU-preempt batches processed thus far * for debug and statistics. */ long rcu_batches_completed_preempt(void) { return rcu_preempt_state.completed; } EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt); /* * Return the number of RCU batches processed thus far for debug & stats. */ long rcu_batches_completed(void) { return rcu_batches_completed_preempt(); } EXPORT_SYMBOL_GPL(rcu_batches_completed); /* |
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* Force a quiescent state for preemptible RCU. */ void rcu_force_quiescent_state(void) { |
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force_quiescent_state(&rcu_preempt_state); |
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} EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); /* |
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* Record a preemptible-RCU quiescent state for the specified CPU. Note |
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* that this just means that the task currently running on the CPU is * not in a quiescent state. There might be any number of tasks blocked * while in an RCU read-side critical section. |
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* * Unlike the other rcu_*_qs() functions, callers to this function * must disable irqs in order to protect the assignment to * ->rcu_read_unlock_special. |
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*/ |
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static void rcu_preempt_qs(int cpu) |
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{ struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu); |
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|
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if (rdp->passed_quiesce == 0) |
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trace_rcu_grace_period("rcu_preempt", rdp->gpnum, "cpuqs"); |
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rdp->passed_quiesce = 1; |
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current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; |
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} /* |
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* We have entered the scheduler, and the current task might soon be * context-switched away from. If this task is in an RCU read-side * critical section, we will no longer be able to rely on the CPU to |
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* record that fact, so we enqueue the task on the blkd_tasks list. * The task will dequeue itself when it exits the outermost enclosing * RCU read-side critical section. Therefore, the current grace period * cannot be permitted to complete until the blkd_tasks list entries * predating the current grace period drain, in other words, until * rnp->gp_tasks becomes NULL. |
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* * Caller must disable preemption. |
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*/ |
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static void rcu_preempt_note_context_switch(int cpu) |
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{ struct task_struct *t = current; |
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unsigned long flags; |
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struct rcu_data *rdp; struct rcu_node *rnp; |
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if (t->rcu_read_lock_nesting > 0 && |
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(t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { /* Possibly blocking in an RCU read-side critical section. */ |
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rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu); |
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rnp = rdp->mynode; |
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raw_spin_lock_irqsave(&rnp->lock, flags); |
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t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; |
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t->rcu_blocked_node = rnp; |
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/* * If this CPU has already checked in, then this task * will hold up the next grace period rather than the * current grace period. Queue the task accordingly. * If the task is queued for the current grace period * (i.e., this CPU has not yet passed through a quiescent * state for the current grace period), then as long * as that task remains queued, the current grace period |
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* cannot end. Note that there is some uncertainty as * to exactly when the current grace period started. * We take a conservative approach, which can result * in unnecessarily waiting on tasks that started very * slightly after the current grace period began. C'est * la vie!!! |
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* * But first, note that the current CPU must still be * on line! |
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*/ |
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WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0); |
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WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); |
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if ((rnp->qsmask & rdp->grpmask) && rnp->gp_tasks != NULL) { list_add(&t->rcu_node_entry, rnp->gp_tasks->prev); rnp->gp_tasks = &t->rcu_node_entry; |
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#ifdef CONFIG_RCU_BOOST if (rnp->boost_tasks != NULL) rnp->boost_tasks = rnp->gp_tasks; #endif /* #ifdef CONFIG_RCU_BOOST */ |
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} else { list_add(&t->rcu_node_entry, &rnp->blkd_tasks); if (rnp->qsmask & rdp->grpmask) rnp->gp_tasks = &t->rcu_node_entry; } |
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trace_rcu_preempt_task(rdp->rsp->name, t->pid, (rnp->qsmask & rdp->grpmask) ? rnp->gpnum : rnp->gpnum + 1); |
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raw_spin_unlock_irqrestore(&rnp->lock, flags); |
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} else if (t->rcu_read_lock_nesting < 0 && t->rcu_read_unlock_special) { /* * Complete exit from RCU read-side critical section on * behalf of preempted instance of __rcu_read_unlock(). */ rcu_read_unlock_special(t); |
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} /* * Either we were not in an RCU read-side critical section to * begin with, or we have now recorded that critical section * globally. Either way, we can now note a quiescent state * for this CPU. Again, if we were in an RCU read-side critical * section, and if that critical section was blocking the current * grace period, then the fact that the task has been enqueued * means that we continue to block the current grace period. */ |
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local_irq_save(flags); |
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rcu_preempt_qs(cpu); |
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local_irq_restore(flags); |
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} /* |
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* Check for preempted RCU readers blocking the current grace period * for the specified rcu_node structure. If the caller needs a reliable * answer, it must hold the rcu_node's ->lock. */ |
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static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
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{ |
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return rnp->gp_tasks != NULL; |
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} |
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/* * Record a quiescent state for all tasks that were previously queued * on the specified rcu_node structure and that were blocking the current * RCU grace period. The caller must hold the specified rnp->lock with * irqs disabled, and this lock is released upon return, but irqs remain * disabled. */ |
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static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) |
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__releases(rnp->lock) { unsigned long mask; struct rcu_node *rnp_p; |
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if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
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raw_spin_unlock_irqrestore(&rnp->lock, flags); |
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return; /* Still need more quiescent states! */ } rnp_p = rnp->parent; if (rnp_p == NULL) { /* * Either there is only one rcu_node in the tree, * or tasks were kicked up to root rcu_node due to * CPUs going offline. */ |
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rcu_report_qs_rsp(&rcu_preempt_state, flags); |
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return; } /* Report up the rest of the hierarchy. */ mask = rnp->grpmask; |
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raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ raw_spin_lock(&rnp_p->lock); /* irqs already disabled. */ |
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rcu_report_qs_rnp(mask, &rcu_preempt_state, rnp_p, flags); |
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} /* |
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* Advance a ->blkd_tasks-list pointer to the next entry, instead * returning NULL if at the end of the list. */ static struct list_head *rcu_next_node_entry(struct task_struct *t, struct rcu_node *rnp) { struct list_head *np; np = t->rcu_node_entry.next; if (np == &rnp->blkd_tasks) np = NULL; return np; } /* |
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* Handle special cases during rcu_read_unlock(), such as needing to * notify RCU core processing or task having blocked during the RCU * read-side critical section. */ |
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void rcu_read_unlock_special(struct task_struct *t) |
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{ int empty; |
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int empty_exp; |
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int empty_exp_now; |
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unsigned long flags; |
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struct list_head *np; |
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#ifdef CONFIG_RCU_BOOST struct rt_mutex *rbmp = NULL; #endif /* #ifdef CONFIG_RCU_BOOST */ |
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struct rcu_node *rnp; int special; /* NMI handlers cannot block and cannot safely manipulate state. */ if (in_nmi()) return; local_irq_save(flags); /* * If RCU core is waiting for this CPU to exit critical section, * let it know that we have done so. */ special = t->rcu_read_unlock_special; if (special & RCU_READ_UNLOCK_NEED_QS) { |
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rcu_preempt_qs(smp_processor_id()); |
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} /* Hardware IRQ handlers cannot block. */ |
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if (in_irq() || in_serving_softirq()) { |
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local_irq_restore(flags); return; } /* Clean up if blocked during RCU read-side critical section. */ if (special & RCU_READ_UNLOCK_BLOCKED) { t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; |
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/* * Remove this task from the list it blocked on. The * task can migrate while we acquire the lock, but at * most one time. So at most two passes through loop. */ for (;;) { |
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rnp = t->rcu_blocked_node; |
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raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
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if (rnp == t->rcu_blocked_node) |
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break; |
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raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
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} |
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empty = !rcu_preempt_blocked_readers_cgp(rnp); |
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empty_exp = !rcu_preempted_readers_exp(rnp); smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */ |
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np = rcu_next_node_entry(t, rnp); |
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list_del_init(&t->rcu_node_entry); |
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t->rcu_blocked_node = NULL; |
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trace_rcu_unlock_preempted_task("rcu_preempt", rnp->gpnum, t->pid); |
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if (&t->rcu_node_entry == rnp->gp_tasks) rnp->gp_tasks = np; if (&t->rcu_node_entry == rnp->exp_tasks) rnp->exp_tasks = np; |
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#ifdef CONFIG_RCU_BOOST if (&t->rcu_node_entry == rnp->boost_tasks) rnp->boost_tasks = np; |
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/* Snapshot/clear ->rcu_boost_mutex with rcu_node lock held. */ if (t->rcu_boost_mutex) { rbmp = t->rcu_boost_mutex; t->rcu_boost_mutex = NULL; |
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} |
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#endif /* #ifdef CONFIG_RCU_BOOST */ |
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/* * If this was the last task on the current list, and if * we aren't waiting on any CPUs, report the quiescent state. |
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* Note that rcu_report_unblock_qs_rnp() releases rnp->lock, * so we must take a snapshot of the expedited state. |
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*/ |
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empty_exp_now = !rcu_preempted_readers_exp(rnp); |
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if (!empty && !rcu_preempt_blocked_readers_cgp(rnp)) { trace_rcu_quiescent_state_report("preempt_rcu", rnp->gpnum, 0, rnp->qsmask, rnp->level, rnp->grplo, rnp->grphi, !!rnp->gp_tasks); |
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rcu_report_unblock_qs_rnp(rnp, flags); |
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} else { |
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raw_spin_unlock_irqrestore(&rnp->lock, flags); |
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} |
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|
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#ifdef CONFIG_RCU_BOOST /* Unboost if we were boosted. */ |
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if (rbmp) rt_mutex_unlock(rbmp); |
27f4d2805 rcu: priority boo... |
438 |
#endif /* #ifdef CONFIG_RCU_BOOST */ |
d9a3da069 rcu: Add expedite... |
439 440 441 442 |
/* * If this was the last task on the expedited lists, * then we need to report up the rcu_node hierarchy. */ |
389abd48e rcu: Avoid RCU-pr... |
443 |
if (!empty_exp && empty_exp_now) |
b40d293eb rcu: Omit self-aw... |
444 |
rcu_report_exp_rnp(&rcu_preempt_state, rnp, true); |
b668c9cf3 rcu: Fix grace-pe... |
445 446 |
} else { local_irq_restore(flags); |
f41d911f8 rcu: Merge preemp... |
447 |
} |
f41d911f8 rcu: Merge preemp... |
448 |
} |
1ed509a22 rcu: Add RCU_CPU_... |
449 450 451 452 453 454 455 456 457 |
#ifdef CONFIG_RCU_CPU_STALL_VERBOSE /* * Dump detailed information for all tasks blocking the current RCU * grace period on the specified rcu_node structure. */ static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp) { unsigned long flags; |
1ed509a22 rcu: Add RCU_CPU_... |
458 |
struct task_struct *t; |
12f5f524c rcu: merge TREE_P... |
459 |
raw_spin_lock_irqsave(&rnp->lock, flags); |
5fd4dc068 rcu: Avoid rcu_pr... |
460 461 462 463 |
if (!rcu_preempt_blocked_readers_cgp(rnp)) { raw_spin_unlock_irqrestore(&rnp->lock, flags); return; } |
12f5f524c rcu: merge TREE_P... |
464 465 466 467 468 |
t = list_entry(rnp->gp_tasks, struct task_struct, rcu_node_entry); list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) sched_show_task(t); raw_spin_unlock_irqrestore(&rnp->lock, flags); |
1ed509a22 rcu: Add RCU_CPU_... |
469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 |
} /* * Dump detailed information for all tasks blocking the current RCU * grace period. */ static void rcu_print_detail_task_stall(struct rcu_state *rsp) { struct rcu_node *rnp = rcu_get_root(rsp); rcu_print_detail_task_stall_rnp(rnp); rcu_for_each_leaf_node(rsp, rnp) rcu_print_detail_task_stall_rnp(rnp); } #else /* #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */ static void rcu_print_detail_task_stall(struct rcu_state *rsp) { } #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */ |
a858af287 rcu: Print schedu... |
491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 |
#ifdef CONFIG_RCU_CPU_STALL_INFO static void rcu_print_task_stall_begin(struct rcu_node *rnp) { printk(KERN_ERR "\tTasks blocked on level-%d rcu_node (CPUs %d-%d):", rnp->level, rnp->grplo, rnp->grphi); } static void rcu_print_task_stall_end(void) { printk(KERN_CONT " "); } #else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ static void rcu_print_task_stall_begin(struct rcu_node *rnp) { } static void rcu_print_task_stall_end(void) { } #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ |
f41d911f8 rcu: Merge preemp... |
516 517 518 519 |
/* * Scan the current list of tasks blocked within RCU read-side critical * sections, printing out the tid of each. */ |
9bc8b5586 rcu: Suppress NMI... |
520 |
static int rcu_print_task_stall(struct rcu_node *rnp) |
f41d911f8 rcu: Merge preemp... |
521 |
{ |
f41d911f8 rcu: Merge preemp... |
522 |
struct task_struct *t; |
9bc8b5586 rcu: Suppress NMI... |
523 |
int ndetected = 0; |
f41d911f8 rcu: Merge preemp... |
524 |
|
27f4d2805 rcu: priority boo... |
525 |
if (!rcu_preempt_blocked_readers_cgp(rnp)) |
9bc8b5586 rcu: Suppress NMI... |
526 |
return 0; |
a858af287 rcu: Print schedu... |
527 |
rcu_print_task_stall_begin(rnp); |
12f5f524c rcu: merge TREE_P... |
528 529 |
t = list_entry(rnp->gp_tasks, struct task_struct, rcu_node_entry); |
9bc8b5586 rcu: Suppress NMI... |
530 |
list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { |
a858af287 rcu: Print schedu... |
531 |
printk(KERN_CONT " P%d", t->pid); |
9bc8b5586 rcu: Suppress NMI... |
532 533 |
ndetected++; } |
a858af287 rcu: Print schedu... |
534 |
rcu_print_task_stall_end(); |
9bc8b5586 rcu: Suppress NMI... |
535 |
return ndetected; |
f41d911f8 rcu: Merge preemp... |
536 |
} |
53d84e004 rcu: permit suppr... |
537 |
/* |
b0e165c03 rcu: Add debug ch... |
538 539 540 541 542 |
* Check that the list of blocked tasks for the newly completed grace * period is in fact empty. It is a serious bug to complete a grace * period that still has RCU readers blocked! This function must be * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock * must be held by the caller. |
12f5f524c rcu: merge TREE_P... |
543 544 545 |
* * Also, if there are blocked tasks on the list, they automatically * block the newly created grace period, so set up ->gp_tasks accordingly. |
b0e165c03 rcu: Add debug ch... |
546 547 548 |
*/ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) { |
27f4d2805 rcu: priority boo... |
549 |
WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); |
12f5f524c rcu: merge TREE_P... |
550 551 |
if (!list_empty(&rnp->blkd_tasks)) rnp->gp_tasks = rnp->blkd_tasks.next; |
28ecd5802 rcu: Add WARN_ON_... |
552 |
WARN_ON_ONCE(rnp->qsmask); |
b0e165c03 rcu: Add debug ch... |
553 |
} |
33f76148c rcu: Add CPU-offl... |
554 555 556 |
#ifdef CONFIG_HOTPLUG_CPU /* |
dd5d19baf rcu: Create rcutr... |
557 558 559 560 561 |
* Handle tasklist migration for case in which all CPUs covered by the * specified rcu_node have gone offline. Move them up to the root * rcu_node. The reason for not just moving them to the immediate * parent is to remove the need for rcu_read_unlock_special() to * make more than two attempts to acquire the target rcu_node's lock. |
b668c9cf3 rcu: Fix grace-pe... |
562 563 |
* Returns true if there were tasks blocking the current RCU grace * period. |
dd5d19baf rcu: Create rcutr... |
564 |
* |
237c80c5c rcu: Fix TREE_PRE... |
565 566 567 |
* Returns 1 if there was previously a task blocking the current grace * period on the specified rcu_node structure. * |
dd5d19baf rcu: Create rcutr... |
568 569 |
* The caller must hold rnp->lock with irqs disabled. */ |
237c80c5c rcu: Fix TREE_PRE... |
570 571 572 |
static int rcu_preempt_offline_tasks(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
dd5d19baf rcu: Create rcutr... |
573 |
{ |
dd5d19baf rcu: Create rcutr... |
574 575 |
struct list_head *lp; struct list_head *lp_root; |
d9a3da069 rcu: Add expedite... |
576 |
int retval = 0; |
dd5d19baf rcu: Create rcutr... |
577 |
struct rcu_node *rnp_root = rcu_get_root(rsp); |
12f5f524c rcu: merge TREE_P... |
578 |
struct task_struct *t; |
dd5d19baf rcu: Create rcutr... |
579 |
|
868489660 rcu: Changes from... |
580 581 |
if (rnp == rnp_root) { WARN_ONCE(1, "Last CPU thought to be offlined?"); |
237c80c5c rcu: Fix TREE_PRE... |
582 |
return 0; /* Shouldn't happen: at least one CPU online. */ |
868489660 rcu: Changes from... |
583 |
} |
12f5f524c rcu: merge TREE_P... |
584 585 586 |
/* If we are on an internal node, complain bitterly. */ WARN_ON_ONCE(rnp != rdp->mynode); |
dd5d19baf rcu: Create rcutr... |
587 588 |
/* |
12f5f524c rcu: merge TREE_P... |
589 590 591 592 593 594 595 |
* Move tasks up to root rcu_node. Don't try to get fancy for * this corner-case operation -- just put this node's tasks * at the head of the root node's list, and update the root node's * ->gp_tasks and ->exp_tasks pointers to those of this node's, * if non-NULL. This might result in waiting for more tasks than * absolutely necessary, but this is a good performance/complexity * tradeoff. |
dd5d19baf rcu: Create rcutr... |
596 |
*/ |
2036d94a7 rcu: Rework detec... |
597 |
if (rcu_preempt_blocked_readers_cgp(rnp) && rnp->qsmask == 0) |
d9a3da069 rcu: Add expedite... |
598 599 600 |
retval |= RCU_OFL_TASKS_NORM_GP; if (rcu_preempted_readers_exp(rnp)) retval |= RCU_OFL_TASKS_EXP_GP; |
12f5f524c rcu: merge TREE_P... |
601 602 603 604 605 606 607 608 609 610 611 612 |
lp = &rnp->blkd_tasks; lp_root = &rnp_root->blkd_tasks; while (!list_empty(lp)) { t = list_entry(lp->next, typeof(*t), rcu_node_entry); raw_spin_lock(&rnp_root->lock); /* irqs already disabled */ list_del(&t->rcu_node_entry); t->rcu_blocked_node = rnp_root; list_add(&t->rcu_node_entry, lp_root); if (&t->rcu_node_entry == rnp->gp_tasks) rnp_root->gp_tasks = rnp->gp_tasks; if (&t->rcu_node_entry == rnp->exp_tasks) rnp_root->exp_tasks = rnp->exp_tasks; |
27f4d2805 rcu: priority boo... |
613 614 615 616 |
#ifdef CONFIG_RCU_BOOST if (&t->rcu_node_entry == rnp->boost_tasks) rnp_root->boost_tasks = rnp->boost_tasks; #endif /* #ifdef CONFIG_RCU_BOOST */ |
12f5f524c rcu: merge TREE_P... |
617 |
raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */ |
dd5d19baf rcu: Create rcutr... |
618 |
} |
27f4d2805 rcu: priority boo... |
619 |
|
1e3fd2b38 rcu: Properly ini... |
620 621 |
rnp->gp_tasks = NULL; rnp->exp_tasks = NULL; |
27f4d2805 rcu: priority boo... |
622 |
#ifdef CONFIG_RCU_BOOST |
1e3fd2b38 rcu: Properly ini... |
623 |
rnp->boost_tasks = NULL; |
5cc900cf5 rcu: Improve boos... |
624 625 626 627 628 |
/* * In case root is being boosted and leaf was not. Make sure * that we boost the tasks blocking the current grace period * in this case. */ |
27f4d2805 rcu: priority boo... |
629 630 |
raw_spin_lock(&rnp_root->lock); /* irqs already disabled */ if (rnp_root->boost_tasks != NULL && |
5cc900cf5 rcu: Improve boos... |
631 632 |
rnp_root->boost_tasks != rnp_root->gp_tasks && rnp_root->boost_tasks != rnp_root->exp_tasks) |
27f4d2805 rcu: priority boo... |
633 634 635 |
rnp_root->boost_tasks = rnp_root->gp_tasks; raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */ #endif /* #ifdef CONFIG_RCU_BOOST */ |
237c80c5c rcu: Fix TREE_PRE... |
636 |
return retval; |
dd5d19baf rcu: Create rcutr... |
637 |
} |
e56014000 rcu: Simplify off... |
638 |
#endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
dd5d19baf rcu: Create rcutr... |
639 |
/* |
f41d911f8 rcu: Merge preemp... |
640 641 642 643 644 645 646 647 648 649 650 |
* Check for a quiescent state from the current CPU. When a task blocks, * the task is recorded in the corresponding CPU's rcu_node structure, * which is checked elsewhere. * * Caller must disable hard irqs. */ static void rcu_preempt_check_callbacks(int cpu) { struct task_struct *t = current; if (t->rcu_read_lock_nesting == 0) { |
c3422bea5 rcu: Simplify rcu... |
651 |
rcu_preempt_qs(cpu); |
f41d911f8 rcu: Merge preemp... |
652 653 |
return; } |
10f39bb1b rcu: protect __rc... |
654 655 |
if (t->rcu_read_lock_nesting > 0 && per_cpu(rcu_preempt_data, cpu).qs_pending) |
c3422bea5 rcu: Simplify rcu... |
656 |
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; |
f41d911f8 rcu: Merge preemp... |
657 |
} |
a46e0899e rcu: use softirq ... |
658 |
#ifdef CONFIG_RCU_BOOST |
09223371d rcu: Use softirq ... |
659 660 661 662 |
static void rcu_preempt_do_callbacks(void) { rcu_do_batch(&rcu_preempt_state, &__get_cpu_var(rcu_preempt_data)); } |
a46e0899e rcu: use softirq ... |
663 |
#endif /* #ifdef CONFIG_RCU_BOOST */ |
f41d911f8 rcu: Merge preemp... |
664 |
/* |
6cc68793e rcu: fix spelling |
665 |
* Queue a preemptible-RCU callback for invocation after a grace period. |
f41d911f8 rcu: Merge preemp... |
666 667 668 |
*/ void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) { |
3fbfbf7a3 rcu: Add callback... |
669 |
__call_rcu(head, func, &rcu_preempt_state, -1, 0); |
f41d911f8 rcu: Merge preemp... |
670 671 |
} EXPORT_SYMBOL_GPL(call_rcu); |
486e25934 rcu: Avoid waking... |
672 673 674 675 676 677 678 679 680 681 |
/* * Queue an RCU callback for lazy invocation after a grace period. * This will likely be later named something like "call_rcu_lazy()", * but this change will require some way of tagging the lazy RCU * callbacks in the list of pending callbacks. Until then, this * function may only be called from __kfree_rcu(). */ void kfree_call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) { |
3fbfbf7a3 rcu: Add callback... |
682 |
__call_rcu(head, func, &rcu_preempt_state, -1, 1); |
486e25934 rcu: Avoid waking... |
683 684 |
} EXPORT_SYMBOL_GPL(kfree_call_rcu); |
6ebb237be rcu: Re-arrange c... |
685 686 687 688 689 |
/** * synchronize_rcu - wait until a grace period has elapsed. * * Control will return to the caller some time after a full grace * period has elapsed, in other words after all currently executing RCU |
77d8485a8 rcu: improve kern... |
690 691 692 693 694 |
* read-side critical sections have completed. Note, however, that * upon return from synchronize_rcu(), the caller might well be executing * concurrently with new RCU read-side critical sections that began while * synchronize_rcu() was waiting. RCU read-side critical sections are * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. |
f0a0e6f28 rcu: Clarify memo... |
695 696 697 |
* * See the description of synchronize_sched() for more detailed information * on memory ordering guarantees. |
6ebb237be rcu: Re-arrange c... |
698 699 700 |
*/ void synchronize_rcu(void) { |
fe15d706c rcu: Add lockdep-... |
701 702 703 704 |
rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && !lock_is_held(&rcu_lock_map) && !lock_is_held(&rcu_sched_lock_map), "Illegal synchronize_rcu() in RCU read-side critical section"); |
6ebb237be rcu: Re-arrange c... |
705 706 |
if (!rcu_scheduler_active) return; |
3705b88db rcu: Add a module... |
707 708 709 710 |
if (rcu_expedited) synchronize_rcu_expedited(); else wait_rcu_gp(call_rcu); |
6ebb237be rcu: Re-arrange c... |
711 712 |
} EXPORT_SYMBOL_GPL(synchronize_rcu); |
d9a3da069 rcu: Add expedite... |
713 |
static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq); |
bcfa57ce1 rcu: Eliminate si... |
714 |
static unsigned long sync_rcu_preempt_exp_count; |
d9a3da069 rcu: Add expedite... |
715 716 717 718 719 720 721 722 723 724 |
static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex); /* * Return non-zero if there are any tasks in RCU read-side critical * sections blocking the current preemptible-RCU expedited grace period. * If there is no preemptible-RCU expedited grace period currently in * progress, returns zero unconditionally. */ static int rcu_preempted_readers_exp(struct rcu_node *rnp) { |
12f5f524c rcu: merge TREE_P... |
725 |
return rnp->exp_tasks != NULL; |
d9a3da069 rcu: Add expedite... |
726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 |
} /* * return non-zero if there is no RCU expedited grace period in progress * for the specified rcu_node structure, in other words, if all CPUs and * tasks covered by the specified rcu_node structure have done their bit * for the current expedited grace period. Works only for preemptible * RCU -- other RCU implementation use other means. * * Caller must hold sync_rcu_preempt_exp_mutex. */ static int sync_rcu_preempt_exp_done(struct rcu_node *rnp) { return !rcu_preempted_readers_exp(rnp) && ACCESS_ONCE(rnp->expmask) == 0; } /* * Report the exit from RCU read-side critical section for the last task * that queued itself during or before the current expedited preemptible-RCU * grace period. This event is reported either to the rcu_node structure on * which the task was queued or to one of that rcu_node structure's ancestors, * recursively up the tree. (Calm down, calm down, we do the recursion * iteratively!) * |
b40d293eb rcu: Omit self-aw... |
751 752 753 |
* Most callers will set the "wake" flag, but the task initiating the * expedited grace period need not wake itself. * |
d9a3da069 rcu: Add expedite... |
754 755 |
* Caller must hold sync_rcu_preempt_exp_mutex. */ |
b40d293eb rcu: Omit self-aw... |
756 757 |
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, bool wake) |
d9a3da069 rcu: Add expedite... |
758 759 760 |
{ unsigned long flags; unsigned long mask; |
1304afb22 rcu: Convert to r... |
761 |
raw_spin_lock_irqsave(&rnp->lock, flags); |
d9a3da069 rcu: Add expedite... |
762 |
for (;;) { |
131906b00 rcu: decrease rcu... |
763 764 |
if (!sync_rcu_preempt_exp_done(rnp)) { raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d9a3da069 rcu: Add expedite... |
765 |
break; |
131906b00 rcu: decrease rcu... |
766 |
} |
d9a3da069 rcu: Add expedite... |
767 |
if (rnp->parent == NULL) { |
131906b00 rcu: decrease rcu... |
768 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); |
b40d293eb rcu: Omit self-aw... |
769 770 |
if (wake) wake_up(&sync_rcu_preempt_exp_wq); |
d9a3da069 rcu: Add expedite... |
771 772 773 |
break; } mask = rnp->grpmask; |
1304afb22 rcu: Convert to r... |
774 |
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
d9a3da069 rcu: Add expedite... |
775 |
rnp = rnp->parent; |
1304afb22 rcu: Convert to r... |
776 |
raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
d9a3da069 rcu: Add expedite... |
777 778 |
rnp->expmask &= ~mask; } |
d9a3da069 rcu: Add expedite... |
779 780 781 782 783 784 785 |
} /* * Snapshot the tasks blocking the newly started preemptible-RCU expedited * grace period for the specified rcu_node structure. If there are no such * tasks, report it up the rcu_node hierarchy. * |
7b2e6011f rcu: Rename ->ono... |
786 787 |
* Caller must hold sync_rcu_preempt_exp_mutex and must exclude * CPU hotplug operations. |
d9a3da069 rcu: Add expedite... |
788 789 790 791 |
*/ static void sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp) { |
1217ed1ba rcu: permit rcu_r... |
792 |
unsigned long flags; |
12f5f524c rcu: merge TREE_P... |
793 |
int must_wait = 0; |
d9a3da069 rcu: Add expedite... |
794 |
|
1217ed1ba rcu: permit rcu_r... |
795 |
raw_spin_lock_irqsave(&rnp->lock, flags); |
c701d5d9b rcu: Fix code-sty... |
796 |
if (list_empty(&rnp->blkd_tasks)) { |
1217ed1ba rcu: permit rcu_r... |
797 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); |
c701d5d9b rcu: Fix code-sty... |
798 |
} else { |
12f5f524c rcu: merge TREE_P... |
799 |
rnp->exp_tasks = rnp->blkd_tasks.next; |
1217ed1ba rcu: permit rcu_r... |
800 |
rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
12f5f524c rcu: merge TREE_P... |
801 802 |
must_wait = 1; } |
d9a3da069 rcu: Add expedite... |
803 |
if (!must_wait) |
b40d293eb rcu: Omit self-aw... |
804 |
rcu_report_exp_rnp(rsp, rnp, false); /* Don't wake self. */ |
d9a3da069 rcu: Add expedite... |
805 |
} |
236fefafe rcu: Call out dan... |
806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 |
/** * synchronize_rcu_expedited - Brute-force RCU grace period * * Wait for an RCU-preempt grace period, but expedite it. The basic * idea is to invoke synchronize_sched_expedited() to push all the tasks to * the ->blkd_tasks lists and wait for this list to drain. This consumes * significant time on all CPUs and is unfriendly to real-time workloads, * so is thus not recommended for any sort of common-case code. * In fact, if you are using synchronize_rcu_expedited() in a loop, * please restructure your code to batch your updates, and then Use a * single synchronize_rcu() instead. * * Note that it is illegal to call this function while holding any lock * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal * to call this function from a CPU-hotplug notifier. Failing to observe * these restriction will result in deadlock. |
019129d59 rcu: Stopgap fix ... |
822 823 824 |
*/ void synchronize_rcu_expedited(void) { |
d9a3da069 rcu: Add expedite... |
825 826 827 |
unsigned long flags; struct rcu_node *rnp; struct rcu_state *rsp = &rcu_preempt_state; |
bcfa57ce1 rcu: Eliminate si... |
828 |
unsigned long snap; |
d9a3da069 rcu: Add expedite... |
829 830 831 832 833 834 835 |
int trycount = 0; smp_mb(); /* Caller's modifications seen first by other CPUs. */ snap = ACCESS_ONCE(sync_rcu_preempt_exp_count) + 1; smp_mb(); /* Above access cannot bleed into critical section. */ /* |
1943c89de rcu: Reduce synch... |
836 837 838 839 840 841 842 843 844 845 |
* Block CPU-hotplug operations. This means that any CPU-hotplug * operation that finds an rcu_node structure with tasks in the * process of being boosted will know that all tasks blocking * this expedited grace period will already be in the process of * being boosted. This simplifies the process of moving tasks * from leaf to root rcu_node structures. */ get_online_cpus(); /* |
d9a3da069 rcu: Add expedite... |
846 847 848 849 850 |
* Acquire lock, falling back to synchronize_rcu() if too many * lock-acquisition failures. Of course, if someone does the * expedited grace period for us, just leave. */ while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) { |
1943c89de rcu: Reduce synch... |
851 852 853 854 855 |
if (ULONG_CMP_LT(snap, ACCESS_ONCE(sync_rcu_preempt_exp_count))) { put_online_cpus(); goto mb_ret; /* Others did our work for us. */ } |
c701d5d9b rcu: Fix code-sty... |
856 |
if (trycount++ < 10) { |
d9a3da069 rcu: Add expedite... |
857 |
udelay(trycount * num_online_cpus()); |
c701d5d9b rcu: Fix code-sty... |
858 |
} else { |
1943c89de rcu: Reduce synch... |
859 |
put_online_cpus(); |
3705b88db rcu: Add a module... |
860 |
wait_rcu_gp(call_rcu); |
d9a3da069 rcu: Add expedite... |
861 862 |
return; } |
d9a3da069 rcu: Add expedite... |
863 |
} |
1943c89de rcu: Reduce synch... |
864 865 |
if (ULONG_CMP_LT(snap, ACCESS_ONCE(sync_rcu_preempt_exp_count))) { put_online_cpus(); |
d9a3da069 rcu: Add expedite... |
866 |
goto unlock_mb_ret; /* Others did our work for us. */ |
1943c89de rcu: Reduce synch... |
867 |
} |
d9a3da069 rcu: Add expedite... |
868 |
|
12f5f524c rcu: merge TREE_P... |
869 |
/* force all RCU readers onto ->blkd_tasks lists. */ |
d9a3da069 rcu: Add expedite... |
870 |
synchronize_sched_expedited(); |
d9a3da069 rcu: Add expedite... |
871 872 |
/* Initialize ->expmask for all non-leaf rcu_node structures. */ rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) { |
1943c89de rcu: Reduce synch... |
873 |
raw_spin_lock_irqsave(&rnp->lock, flags); |
d9a3da069 rcu: Add expedite... |
874 |
rnp->expmask = rnp->qsmaskinit; |
1943c89de rcu: Reduce synch... |
875 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d9a3da069 rcu: Add expedite... |
876 |
} |
12f5f524c rcu: merge TREE_P... |
877 |
/* Snapshot current state of ->blkd_tasks lists. */ |
d9a3da069 rcu: Add expedite... |
878 879 880 881 |
rcu_for_each_leaf_node(rsp, rnp) sync_rcu_preempt_exp_init(rsp, rnp); if (NUM_RCU_NODES > 1) sync_rcu_preempt_exp_init(rsp, rcu_get_root(rsp)); |
1943c89de rcu: Reduce synch... |
882 |
put_online_cpus(); |
d9a3da069 rcu: Add expedite... |
883 |
|
12f5f524c rcu: merge TREE_P... |
884 |
/* Wait for snapshotted ->blkd_tasks lists to drain. */ |
d9a3da069 rcu: Add expedite... |
885 886 887 888 889 890 891 892 893 894 895 |
rnp = rcu_get_root(rsp); wait_event(sync_rcu_preempt_exp_wq, sync_rcu_preempt_exp_done(rnp)); /* Clean up and exit. */ smp_mb(); /* ensure expedited GP seen before counter increment. */ ACCESS_ONCE(sync_rcu_preempt_exp_count)++; unlock_mb_ret: mutex_unlock(&sync_rcu_preempt_exp_mutex); mb_ret: smp_mb(); /* ensure subsequent action seen after grace period. */ |
019129d59 rcu: Stopgap fix ... |
896 897 |
} EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); |
e74f4c456 rcu: Make hot-unp... |
898 899 |
/** * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. |
f0a0e6f28 rcu: Clarify memo... |
900 901 902 903 904 |
* * Note that this primitive does not necessarily wait for an RCU grace period * to complete. For example, if there are no RCU callbacks queued anywhere * in the system, then rcu_barrier() is within its rights to return * immediately, without waiting for anything, much less an RCU grace period. |
e74f4c456 rcu: Make hot-unp... |
905 906 907 |
*/ void rcu_barrier(void) { |
037b64ed0 rcu: Place pointe... |
908 |
_rcu_barrier(&rcu_preempt_state); |
e74f4c456 rcu: Make hot-unp... |
909 910 |
} EXPORT_SYMBOL_GPL(rcu_barrier); |
f41d911f8 rcu: Merge preemp... |
911 |
/* |
6cc68793e rcu: fix spelling |
912 |
* Initialize preemptible RCU's state structures. |
1eba8f843 rcu: Clean up cod... |
913 914 915 |
*/ static void __init __rcu_init_preempt(void) { |
394f99a90 rcu: simplify the... |
916 |
rcu_init_one(&rcu_preempt_state, &rcu_preempt_data); |
1eba8f843 rcu: Clean up cod... |
917 |
} |
f41d911f8 rcu: Merge preemp... |
918 |
#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ |
27f4d2805 rcu: priority boo... |
919 |
static struct rcu_state *rcu_state = &rcu_sched_state; |
f41d911f8 rcu: Merge preemp... |
920 921 922 |
/* * Tell them what RCU they are running. */ |
0e0fc1c23 rcu: Mark init-ti... |
923 |
static void __init rcu_bootup_announce(void) |
f41d911f8 rcu: Merge preemp... |
924 925 926 |
{ printk(KERN_INFO "Hierarchical RCU implementation. "); |
26845c286 rcu: print boot-t... |
927 |
rcu_bootup_announce_oddness(); |
f41d911f8 rcu: Merge preemp... |
928 929 930 931 932 933 934 935 936 937 938 939 |
} /* * Return the number of RCU batches processed thus far for debug & stats. */ long rcu_batches_completed(void) { return rcu_batches_completed_sched(); } EXPORT_SYMBOL_GPL(rcu_batches_completed); /* |
bf66f18e7 rcu: Add force_qu... |
940 941 942 943 944 945 946 947 948 949 |
* Force a quiescent state for RCU, which, because there is no preemptible * RCU, becomes the same as rcu-sched. */ void rcu_force_quiescent_state(void) { rcu_sched_force_quiescent_state(); } EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); /* |
cba6d0d64 Revert "rcu: Move... |
950 951 952 953 954 955 956 957 |
* Because preemptible RCU does not exist, we never have to check for * CPUs being in quiescent states. */ static void rcu_preempt_note_context_switch(int cpu) { } /* |
6cc68793e rcu: fix spelling |
958 |
* Because preemptible RCU does not exist, there are never any preempted |
fc2219d49 rcu: Clean up cod... |
959 960 |
* RCU readers. */ |
27f4d2805 rcu: priority boo... |
961 |
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
fc2219d49 rcu: Clean up cod... |
962 963 964 |
{ return 0; } |
b668c9cf3 rcu: Fix grace-pe... |
965 966 967 |
#ifdef CONFIG_HOTPLUG_CPU /* Because preemptible RCU does not exist, no quieting of tasks. */ |
d3f6bad39 rcu: Rename "quie... |
968 |
static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) |
b668c9cf3 rcu: Fix grace-pe... |
969 |
{ |
1304afb22 rcu: Convert to r... |
970 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); |
b668c9cf3 rcu: Fix grace-pe... |
971 972 973 |
} #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
f41d911f8 rcu: Merge preemp... |
974 |
/* |
6cc68793e rcu: fix spelling |
975 |
* Because preemptible RCU does not exist, we never have to check for |
f41d911f8 rcu: Merge preemp... |
976 977 |
* tasks blocked within RCU read-side critical sections. */ |
1ed509a22 rcu: Add RCU_CPU_... |
978 979 980 981 982 |
static void rcu_print_detail_task_stall(struct rcu_state *rsp) { } /* |
6cc68793e rcu: fix spelling |
983 |
* Because preemptible RCU does not exist, we never have to check for |
1ed509a22 rcu: Add RCU_CPU_... |
984 985 |
* tasks blocked within RCU read-side critical sections. */ |
9bc8b5586 rcu: Suppress NMI... |
986 |
static int rcu_print_task_stall(struct rcu_node *rnp) |
f41d911f8 rcu: Merge preemp... |
987 |
{ |
9bc8b5586 rcu: Suppress NMI... |
988 |
return 0; |
f41d911f8 rcu: Merge preemp... |
989 |
} |
53d84e004 rcu: permit suppr... |
990 |
/* |
6cc68793e rcu: fix spelling |
991 |
* Because there is no preemptible RCU, there can be no readers blocked, |
49e291266 rcu: Fix thinko, ... |
992 993 |
* so there is no need to check for blocked tasks. So check only for * bogus qsmask values. |
b0e165c03 rcu: Add debug ch... |
994 995 996 |
*/ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) { |
49e291266 rcu: Fix thinko, ... |
997 |
WARN_ON_ONCE(rnp->qsmask); |
b0e165c03 rcu: Add debug ch... |
998 |
} |
33f76148c rcu: Add CPU-offl... |
999 1000 1001 |
#ifdef CONFIG_HOTPLUG_CPU /* |
6cc68793e rcu: fix spelling |
1002 |
* Because preemptible RCU does not exist, it never needs to migrate |
237c80c5c rcu: Fix TREE_PRE... |
1003 1004 1005 |
* tasks that were blocked within RCU read-side critical sections, and * such non-existent tasks cannot possibly have been blocking the current * grace period. |
dd5d19baf rcu: Create rcutr... |
1006 |
*/ |
237c80c5c rcu: Fix TREE_PRE... |
1007 1008 1009 |
static int rcu_preempt_offline_tasks(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
dd5d19baf rcu: Create rcutr... |
1010 |
{ |
237c80c5c rcu: Fix TREE_PRE... |
1011 |
return 0; |
dd5d19baf rcu: Create rcutr... |
1012 |
} |
e56014000 rcu: Simplify off... |
1013 |
#endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
dd5d19baf rcu: Create rcutr... |
1014 |
/* |
6cc68793e rcu: fix spelling |
1015 |
* Because preemptible RCU does not exist, it never has any callbacks |
f41d911f8 rcu: Merge preemp... |
1016 1017 |
* to check. */ |
1eba8f843 rcu: Clean up cod... |
1018 |
static void rcu_preempt_check_callbacks(int cpu) |
f41d911f8 rcu: Merge preemp... |
1019 1020 1021 1022 |
{ } /* |
486e25934 rcu: Avoid waking... |
1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 |
* Queue an RCU callback for lazy invocation after a grace period. * This will likely be later named something like "call_rcu_lazy()", * but this change will require some way of tagging the lazy RCU * callbacks in the list of pending callbacks. Until then, this * function may only be called from __kfree_rcu(). * * Because there is no preemptible RCU, we use RCU-sched instead. */ void kfree_call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) { |
3fbfbf7a3 rcu: Add callback... |
1034 |
__call_rcu(head, func, &rcu_sched_state, -1, 1); |
486e25934 rcu: Avoid waking... |
1035 1036 1037 1038 |
} EXPORT_SYMBOL_GPL(kfree_call_rcu); /* |
019129d59 rcu: Stopgap fix ... |
1039 |
* Wait for an rcu-preempt grace period, but make it happen quickly. |
6cc68793e rcu: fix spelling |
1040 |
* But because preemptible RCU does not exist, map to rcu-sched. |
019129d59 rcu: Stopgap fix ... |
1041 1042 1043 1044 1045 1046 |
*/ void synchronize_rcu_expedited(void) { synchronize_sched_expedited(); } EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); |
d9a3da069 rcu: Add expedite... |
1047 1048 1049 |
#ifdef CONFIG_HOTPLUG_CPU /* |
6cc68793e rcu: fix spelling |
1050 |
* Because preemptible RCU does not exist, there is never any need to |
d9a3da069 rcu: Add expedite... |
1051 1052 1053 |
* report on tasks preempted in RCU read-side critical sections during * expedited RCU grace periods. */ |
b40d293eb rcu: Omit self-aw... |
1054 1055 |
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, bool wake) |
d9a3da069 rcu: Add expedite... |
1056 |
{ |
d9a3da069 rcu: Add expedite... |
1057 1058 1059 |
} #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
019129d59 rcu: Stopgap fix ... |
1060 |
/* |
6cc68793e rcu: fix spelling |
1061 |
* Because preemptible RCU does not exist, rcu_barrier() is just |
e74f4c456 rcu: Make hot-unp... |
1062 1063 1064 1065 1066 1067 1068 1069 1070 |
* another name for rcu_barrier_sched(). */ void rcu_barrier(void) { rcu_barrier_sched(); } EXPORT_SYMBOL_GPL(rcu_barrier); /* |
6cc68793e rcu: fix spelling |
1071 |
* Because preemptible RCU does not exist, it need not be initialized. |
1eba8f843 rcu: Clean up cod... |
1072 1073 1074 1075 |
*/ static void __init __rcu_init_preempt(void) { } |
f41d911f8 rcu: Merge preemp... |
1076 |
#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ |
8bd93a2c5 rcu: Accelerate g... |
1077 |
|
27f4d2805 rcu: priority boo... |
1078 1079 1080 |
#ifdef CONFIG_RCU_BOOST #include "rtmutex_common.h" |
0ea1f2ebe rcu: Add boosting... |
1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 |
#ifdef CONFIG_RCU_TRACE static void rcu_initiate_boost_trace(struct rcu_node *rnp) { if (list_empty(&rnp->blkd_tasks)) rnp->n_balk_blkd_tasks++; else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL) rnp->n_balk_exp_gp_tasks++; else if (rnp->gp_tasks != NULL && rnp->boost_tasks != NULL) rnp->n_balk_boost_tasks++; else if (rnp->gp_tasks != NULL && rnp->qsmask != 0) rnp->n_balk_notblocked++; else if (rnp->gp_tasks != NULL && |
a9f4793d8 rcu: fix tracing ... |
1094 |
ULONG_CMP_LT(jiffies, rnp->boost_time)) |
0ea1f2ebe rcu: Add boosting... |
1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 |
rnp->n_balk_notyet++; else rnp->n_balk_nos++; } #else /* #ifdef CONFIG_RCU_TRACE */ static void rcu_initiate_boost_trace(struct rcu_node *rnp) { } #endif /* #else #ifdef CONFIG_RCU_TRACE */ |
5d01bbd11 rcu: Yield simpler |
1107 1108 1109 1110 1111 1112 1113 1114 1115 |
static void rcu_wake_cond(struct task_struct *t, int status) { /* * If the thread is yielding, only wake it when this * is invoked from idle */ if (status != RCU_KTHREAD_YIELDING || is_idle_task(current)) wake_up_process(t); } |
27f4d2805 rcu: priority boo... |
1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 |
/* * Carry out RCU priority boosting on the task indicated by ->exp_tasks * or ->boost_tasks, advancing the pointer to the next task in the * ->blkd_tasks list. * * Note that irqs must be enabled: boosting the task can block. * Returns 1 if there are more tasks needing to be boosted. */ static int rcu_boost(struct rcu_node *rnp) { unsigned long flags; struct rt_mutex mtx; struct task_struct *t; struct list_head *tb; if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) return 0; /* Nothing left to boost. */ raw_spin_lock_irqsave(&rnp->lock, flags); /* * Recheck under the lock: all tasks in need of boosting * might exit their RCU read-side critical sections on their own. */ if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) { raw_spin_unlock_irqrestore(&rnp->lock, flags); return 0; } /* * Preferentially boost tasks blocking expedited grace periods. * This cannot starve the normal grace periods because a second * expedited grace period must boost all blocked tasks, including * those blocking the pre-existing normal grace period. */ |
0ea1f2ebe rcu: Add boosting... |
1151 |
if (rnp->exp_tasks != NULL) { |
27f4d2805 rcu: priority boo... |
1152 |
tb = rnp->exp_tasks; |
0ea1f2ebe rcu: Add boosting... |
1153 1154 |
rnp->n_exp_boosts++; } else { |
27f4d2805 rcu: priority boo... |
1155 |
tb = rnp->boost_tasks; |
0ea1f2ebe rcu: Add boosting... |
1156 1157 1158 |
rnp->n_normal_boosts++; } rnp->n_tasks_boosted++; |
27f4d2805 rcu: priority boo... |
1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 |
/* * We boost task t by manufacturing an rt_mutex that appears to * be held by task t. We leave a pointer to that rt_mutex where * task t can find it, and task t will release the mutex when it * exits its outermost RCU read-side critical section. Then * simply acquiring this artificial rt_mutex will boost task * t's priority. (Thanks to tglx for suggesting this approach!) * * Note that task t must acquire rnp->lock to remove itself from * the ->blkd_tasks list, which it will do from exit() if from * nowhere else. We therefore are guaranteed that task t will * stay around at least until we drop rnp->lock. Note that * rnp->lock also resolves races between our priority boosting * and task t's exiting its outermost RCU read-side critical * section. */ t = container_of(tb, struct task_struct, rcu_node_entry); rt_mutex_init_proxy_locked(&mtx, t); t->rcu_boost_mutex = &mtx; |
27f4d2805 rcu: priority boo... |
1179 1180 1181 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */ rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ |
4f89b336f rcu: Apply ACCESS... |
1182 1183 |
return ACCESS_ONCE(rnp->exp_tasks) != NULL || ACCESS_ONCE(rnp->boost_tasks) != NULL; |
27f4d2805 rcu: priority boo... |
1184 1185 1186 |
} /* |
27f4d2805 rcu: priority boo... |
1187 1188 1189 1190 1191 1192 1193 1194 |
* Priority-boosting kthread. One per leaf rcu_node and one for the * root rcu_node. */ static int rcu_boost_kthread(void *arg) { struct rcu_node *rnp = (struct rcu_node *)arg; int spincnt = 0; int more2boost; |
385680a94 rcu: Add event-tr... |
1195 |
trace_rcu_utilization("Start boost kthread@init"); |
27f4d2805 rcu: priority boo... |
1196 |
for (;;) { |
d71df90ea rcu: add tracing ... |
1197 |
rnp->boost_kthread_status = RCU_KTHREAD_WAITING; |
385680a94 rcu: Add event-tr... |
1198 |
trace_rcu_utilization("End boost kthread@rcu_wait"); |
08bca60a6 rcu: Remove waitq... |
1199 |
rcu_wait(rnp->boost_tasks || rnp->exp_tasks); |
385680a94 rcu: Add event-tr... |
1200 |
trace_rcu_utilization("Start boost kthread@rcu_wait"); |
d71df90ea rcu: add tracing ... |
1201 |
rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; |
27f4d2805 rcu: priority boo... |
1202 1203 1204 1205 1206 1207 |
more2boost = rcu_boost(rnp); if (more2boost) spincnt++; else spincnt = 0; if (spincnt > 10) { |
5d01bbd11 rcu: Yield simpler |
1208 |
rnp->boost_kthread_status = RCU_KTHREAD_YIELDING; |
385680a94 rcu: Add event-tr... |
1209 |
trace_rcu_utilization("End boost kthread@rcu_yield"); |
5d01bbd11 rcu: Yield simpler |
1210 |
schedule_timeout_interruptible(2); |
385680a94 rcu: Add event-tr... |
1211 |
trace_rcu_utilization("Start boost kthread@rcu_yield"); |
27f4d2805 rcu: priority boo... |
1212 1213 1214 |
spincnt = 0; } } |
1217ed1ba rcu: permit rcu_r... |
1215 |
/* NOTREACHED */ |
385680a94 rcu: Add event-tr... |
1216 |
trace_rcu_utilization("End boost kthread@notreached"); |
27f4d2805 rcu: priority boo... |
1217 1218 1219 1220 1221 1222 1223 1224 1225 |
return 0; } /* * Check to see if it is time to start boosting RCU readers that are * blocking the current grace period, and, if so, tell the per-rcu_node * kthread to start boosting them. If there is an expedited grace * period in progress, it is always time to boost. * |
b065a8535 rcu: Fix obsolete... |
1226 1227 1228 |
* The caller must hold rnp->lock, which this function releases. * The ->boost_kthread_task is immortal, so we don't need to worry * about it going away. |
27f4d2805 rcu: priority boo... |
1229 |
*/ |
1217ed1ba rcu: permit rcu_r... |
1230 |
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
27f4d2805 rcu: priority boo... |
1231 1232 |
{ struct task_struct *t; |
0ea1f2ebe rcu: Add boosting... |
1233 1234 |
if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { rnp->n_balk_exp_gp_tasks++; |
1217ed1ba rcu: permit rcu_r... |
1235 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d2805 rcu: priority boo... |
1236 |
return; |
0ea1f2ebe rcu: Add boosting... |
1237 |
} |
27f4d2805 rcu: priority boo... |
1238 1239 1240 1241 1242 1243 1244 |
if (rnp->exp_tasks != NULL || (rnp->gp_tasks != NULL && rnp->boost_tasks == NULL && rnp->qsmask == 0 && ULONG_CMP_GE(jiffies, rnp->boost_time))) { if (rnp->exp_tasks == NULL) rnp->boost_tasks = rnp->gp_tasks; |
1217ed1ba rcu: permit rcu_r... |
1245 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d2805 rcu: priority boo... |
1246 |
t = rnp->boost_kthread_task; |
5d01bbd11 rcu: Yield simpler |
1247 1248 |
if (t) rcu_wake_cond(t, rnp->boost_kthread_status); |
1217ed1ba rcu: permit rcu_r... |
1249 |
} else { |
0ea1f2ebe rcu: Add boosting... |
1250 |
rcu_initiate_boost_trace(rnp); |
1217ed1ba rcu: permit rcu_r... |
1251 1252 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); } |
27f4d2805 rcu: priority boo... |
1253 |
} |
0f962a5e7 rcu: Force per-rc... |
1254 |
/* |
a46e0899e rcu: use softirq ... |
1255 1256 1257 1258 1259 1260 1261 1262 |
* Wake up the per-CPU kthread to invoke RCU callbacks. */ static void invoke_rcu_callbacks_kthread(void) { unsigned long flags; local_irq_save(flags); __this_cpu_write(rcu_cpu_has_work, 1); |
1eb521210 rcu: Avoid unnece... |
1263 |
if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && |
5d01bbd11 rcu: Yield simpler |
1264 1265 1266 1267 |
current != __this_cpu_read(rcu_cpu_kthread_task)) { rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task), __this_cpu_read(rcu_cpu_kthread_status)); } |
a46e0899e rcu: use softirq ... |
1268 1269 1270 1271 |
local_irq_restore(flags); } /* |
dff1672d9 rcu: Keep invokin... |
1272 1273 1274 1275 1276 1277 1278 |
* Is the current CPU running the RCU-callbacks kthread? * Caller must have preemption disabled. */ static bool rcu_is_callbacks_kthread(void) { return __get_cpu_var(rcu_cpu_kthread_task) == current; } |
27f4d2805 rcu: priority boo... |
1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 |
#define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) /* * Do priority-boost accounting for the start of a new grace period. */ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) { rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; } /* |
27f4d2805 rcu: priority boo... |
1290 1291 1292 1293 1294 |
* Create an RCU-boost kthread for the specified node if one does not * already exist. We only create this kthread for preemptible RCU. * Returns zero if all is well, a negated errno otherwise. */ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp, |
5d01bbd11 rcu: Yield simpler |
1295 |
struct rcu_node *rnp) |
27f4d2805 rcu: priority boo... |
1296 |
{ |
5d01bbd11 rcu: Yield simpler |
1297 |
int rnp_index = rnp - &rsp->node[0]; |
27f4d2805 rcu: priority boo... |
1298 1299 1300 1301 1302 1303 |
unsigned long flags; struct sched_param sp; struct task_struct *t; if (&rcu_preempt_state != rsp) return 0; |
5d01bbd11 rcu: Yield simpler |
1304 1305 1306 |
if (!rcu_scheduler_fully_active || rnp->qsmaskinit == 0) return 0; |
a46e0899e rcu: use softirq ... |
1307 |
rsp->boost = 1; |
27f4d2805 rcu: priority boo... |
1308 1309 1310 |
if (rnp->boost_kthread_task != NULL) return 0; t = kthread_create(rcu_boost_kthread, (void *)rnp, |
5b61b0baa rcu: Wire up RCU_... |
1311 |
"rcub/%d", rnp_index); |
27f4d2805 rcu: priority boo... |
1312 1313 1314 1315 1316 |
if (IS_ERR(t)) return PTR_ERR(t); raw_spin_lock_irqsave(&rnp->lock, flags); rnp->boost_kthread_task = t; raw_spin_unlock_irqrestore(&rnp->lock, flags); |
5b61b0baa rcu: Wire up RCU_... |
1317 |
sp.sched_priority = RCU_BOOST_PRIO; |
27f4d2805 rcu: priority boo... |
1318 |
sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
9a4327369 rcu: Simplify cur... |
1319 |
wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ |
27f4d2805 rcu: priority boo... |
1320 1321 |
return 0; } |
f8b7fc6b5 rcu: Move RCU_BOO... |
1322 1323 1324 1325 1326 1327 |
static void rcu_kthread_do_work(void) { rcu_do_batch(&rcu_sched_state, &__get_cpu_var(rcu_sched_data)); rcu_do_batch(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); rcu_preempt_do_callbacks(); } |
62ab70724 rcu: Use smp_hotp... |
1328 |
static void rcu_cpu_kthread_setup(unsigned int cpu) |
f8b7fc6b5 rcu: Move RCU_BOO... |
1329 |
{ |
f8b7fc6b5 rcu: Move RCU_BOO... |
1330 |
struct sched_param sp; |
f8b7fc6b5 rcu: Move RCU_BOO... |
1331 |
|
62ab70724 rcu: Use smp_hotp... |
1332 1333 |
sp.sched_priority = RCU_KTHREAD_PRIO; sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); |
f8b7fc6b5 rcu: Move RCU_BOO... |
1334 |
} |
62ab70724 rcu: Use smp_hotp... |
1335 |
static void rcu_cpu_kthread_park(unsigned int cpu) |
f8b7fc6b5 rcu: Move RCU_BOO... |
1336 |
{ |
62ab70724 rcu: Use smp_hotp... |
1337 |
per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; |
f8b7fc6b5 rcu: Move RCU_BOO... |
1338 |
} |
62ab70724 rcu: Use smp_hotp... |
1339 |
static int rcu_cpu_kthread_should_run(unsigned int cpu) |
f8b7fc6b5 rcu: Move RCU_BOO... |
1340 |
{ |
62ab70724 rcu: Use smp_hotp... |
1341 |
return __get_cpu_var(rcu_cpu_has_work); |
f8b7fc6b5 rcu: Move RCU_BOO... |
1342 1343 1344 1345 |
} /* * Per-CPU kernel thread that invokes RCU callbacks. This replaces the |
e0f23060a rcu: Update comme... |
1346 1347 |
* RCU softirq used in flavors and configurations of RCU that do not * support RCU priority boosting. |
f8b7fc6b5 rcu: Move RCU_BOO... |
1348 |
*/ |
62ab70724 rcu: Use smp_hotp... |
1349 |
static void rcu_cpu_kthread(unsigned int cpu) |
f8b7fc6b5 rcu: Move RCU_BOO... |
1350 |
{ |
62ab70724 rcu: Use smp_hotp... |
1351 1352 1353 |
unsigned int *statusp = &__get_cpu_var(rcu_cpu_kthread_status); char work, *workp = &__get_cpu_var(rcu_cpu_has_work); int spincnt; |
f8b7fc6b5 rcu: Move RCU_BOO... |
1354 |
|
62ab70724 rcu: Use smp_hotp... |
1355 |
for (spincnt = 0; spincnt < 10; spincnt++) { |
385680a94 rcu: Add event-tr... |
1356 |
trace_rcu_utilization("Start CPU kthread@rcu_wait"); |
f8b7fc6b5 rcu: Move RCU_BOO... |
1357 |
local_bh_disable(); |
f8b7fc6b5 rcu: Move RCU_BOO... |
1358 |
*statusp = RCU_KTHREAD_RUNNING; |
62ab70724 rcu: Use smp_hotp... |
1359 1360 |
this_cpu_inc(rcu_cpu_kthread_loops); local_irq_disable(); |
f8b7fc6b5 rcu: Move RCU_BOO... |
1361 1362 |
work = *workp; *workp = 0; |
62ab70724 rcu: Use smp_hotp... |
1363 |
local_irq_enable(); |
f8b7fc6b5 rcu: Move RCU_BOO... |
1364 1365 1366 |
if (work) rcu_kthread_do_work(); local_bh_enable(); |
62ab70724 rcu: Use smp_hotp... |
1367 1368 1369 1370 |
if (*workp == 0) { trace_rcu_utilization("End CPU kthread@rcu_wait"); *statusp = RCU_KTHREAD_WAITING; return; |
f8b7fc6b5 rcu: Move RCU_BOO... |
1371 1372 |
} } |
62ab70724 rcu: Use smp_hotp... |
1373 1374 1375 1376 1377 |
*statusp = RCU_KTHREAD_YIELDING; trace_rcu_utilization("Start CPU kthread@rcu_yield"); schedule_timeout_interruptible(2); trace_rcu_utilization("End CPU kthread@rcu_yield"); *statusp = RCU_KTHREAD_WAITING; |
f8b7fc6b5 rcu: Move RCU_BOO... |
1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 |
} /* * Set the per-rcu_node kthread's affinity to cover all CPUs that are * served by the rcu_node in question. The CPU hotplug lock is still * held, so the value of rnp->qsmaskinit will be stable. * * We don't include outgoingcpu in the affinity set, use -1 if there is * no outgoing CPU. If there are no CPUs left in the affinity set, * this function allows the kthread to execute on any CPU. */ |
5d01bbd11 rcu: Yield simpler |
1389 |
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
f8b7fc6b5 rcu: Move RCU_BOO... |
1390 |
{ |
5d01bbd11 rcu: Yield simpler |
1391 1392 |
struct task_struct *t = rnp->boost_kthread_task; unsigned long mask = rnp->qsmaskinit; |
f8b7fc6b5 rcu: Move RCU_BOO... |
1393 1394 |
cpumask_var_t cm; int cpu; |
f8b7fc6b5 rcu: Move RCU_BOO... |
1395 |
|
5d01bbd11 rcu: Yield simpler |
1396 |
if (!t) |
f8b7fc6b5 rcu: Move RCU_BOO... |
1397 |
return; |
5d01bbd11 rcu: Yield simpler |
1398 |
if (!zalloc_cpumask_var(&cm, GFP_KERNEL)) |
f8b7fc6b5 rcu: Move RCU_BOO... |
1399 |
return; |
f8b7fc6b5 rcu: Move RCU_BOO... |
1400 1401 1402 1403 1404 1405 1406 1407 1408 |
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) if ((mask & 0x1) && cpu != outgoingcpu) cpumask_set_cpu(cpu, cm); if (cpumask_weight(cm) == 0) { cpumask_setall(cm); for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) cpumask_clear_cpu(cpu, cm); WARN_ON_ONCE(cpumask_weight(cm) == 0); } |
5d01bbd11 rcu: Yield simpler |
1409 |
set_cpus_allowed_ptr(t, cm); |
f8b7fc6b5 rcu: Move RCU_BOO... |
1410 1411 |
free_cpumask_var(cm); } |
62ab70724 rcu: Use smp_hotp... |
1412 1413 1414 1415 1416 1417 1418 1419 |
static struct smp_hotplug_thread rcu_cpu_thread_spec = { .store = &rcu_cpu_kthread_task, .thread_should_run = rcu_cpu_kthread_should_run, .thread_fn = rcu_cpu_kthread, .thread_comm = "rcuc/%u", .setup = rcu_cpu_kthread_setup, .park = rcu_cpu_kthread_park, }; |
f8b7fc6b5 rcu: Move RCU_BOO... |
1420 1421 1422 1423 1424 1425 |
/* * Spawn all kthreads -- called as soon as the scheduler is running. */ static int __init rcu_spawn_kthreads(void) { |
f8b7fc6b5 rcu: Move RCU_BOO... |
1426 |
struct rcu_node *rnp; |
5d01bbd11 rcu: Yield simpler |
1427 |
int cpu; |
f8b7fc6b5 rcu: Move RCU_BOO... |
1428 |
|
b0d304172 rcu: Prevent RCU ... |
1429 |
rcu_scheduler_fully_active = 1; |
62ab70724 rcu: Use smp_hotp... |
1430 |
for_each_possible_cpu(cpu) |
f8b7fc6b5 rcu: Move RCU_BOO... |
1431 |
per_cpu(rcu_cpu_has_work, cpu) = 0; |
62ab70724 rcu: Use smp_hotp... |
1432 |
BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec)); |
f8b7fc6b5 rcu: Move RCU_BOO... |
1433 |
rnp = rcu_get_root(rcu_state); |
5d01bbd11 rcu: Yield simpler |
1434 |
(void)rcu_spawn_one_boost_kthread(rcu_state, rnp); |
f8b7fc6b5 rcu: Move RCU_BOO... |
1435 1436 |
if (NUM_RCU_NODES > 1) { rcu_for_each_leaf_node(rcu_state, rnp) |
5d01bbd11 rcu: Yield simpler |
1437 |
(void)rcu_spawn_one_boost_kthread(rcu_state, rnp); |
f8b7fc6b5 rcu: Move RCU_BOO... |
1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 |
} return 0; } early_initcall(rcu_spawn_kthreads); static void __cpuinit rcu_prepare_kthreads(int cpu) { struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); struct rcu_node *rnp = rdp->mynode; /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ |
62ab70724 rcu: Use smp_hotp... |
1449 |
if (rcu_scheduler_fully_active) |
5d01bbd11 rcu: Yield simpler |
1450 |
(void)rcu_spawn_one_boost_kthread(rcu_state, rnp); |
f8b7fc6b5 rcu: Move RCU_BOO... |
1451 |
} |
27f4d2805 rcu: priority boo... |
1452 |
#else /* #ifdef CONFIG_RCU_BOOST */ |
1217ed1ba rcu: permit rcu_r... |
1453 |
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
27f4d2805 rcu: priority boo... |
1454 |
{ |
1217ed1ba rcu: permit rcu_r... |
1455 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d2805 rcu: priority boo... |
1456 |
} |
a46e0899e rcu: use softirq ... |
1457 |
static void invoke_rcu_callbacks_kthread(void) |
27f4d2805 rcu: priority boo... |
1458 |
{ |
a46e0899e rcu: use softirq ... |
1459 |
WARN_ON_ONCE(1); |
27f4d2805 rcu: priority boo... |
1460 |
} |
dff1672d9 rcu: Keep invokin... |
1461 1462 1463 1464 |
static bool rcu_is_callbacks_kthread(void) { return false; } |
27f4d2805 rcu: priority boo... |
1465 1466 1467 |
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) { } |
5d01bbd11 rcu: Yield simpler |
1468 |
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
f8b7fc6b5 rcu: Move RCU_BOO... |
1469 1470 |
{ } |
b0d304172 rcu: Prevent RCU ... |
1471 1472 1473 1474 1475 1476 |
static int __init rcu_scheduler_really_started(void) { rcu_scheduler_fully_active = 1; return 0; } early_initcall(rcu_scheduler_really_started); |
f8b7fc6b5 rcu: Move RCU_BOO... |
1477 1478 1479 |
static void __cpuinit rcu_prepare_kthreads(int cpu) { } |
27f4d2805 rcu: priority boo... |
1480 |
#endif /* #else #ifdef CONFIG_RCU_BOOST */ |
8bd93a2c5 rcu: Accelerate g... |
1481 1482 1483 1484 1485 1486 1487 1488 |
#if !defined(CONFIG_RCU_FAST_NO_HZ) /* * Check to see if any future RCU-related work will need to be done * by the current CPU, even if none need be done immediately, returning * 1 if so. This function is part of the RCU implementation; it is -not- * an exported member of the RCU API. * |
7cb924990 rcu: Permit dynti... |
1489 1490 |
* Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs * any flavor of RCU. |
8bd93a2c5 rcu: Accelerate g... |
1491 |
*/ |
aa9b16306 rcu: Precompute R... |
1492 |
int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies) |
8bd93a2c5 rcu: Accelerate g... |
1493 |
{ |
aa9b16306 rcu: Precompute R... |
1494 |
*delta_jiffies = ULONG_MAX; |
c0f4dfd4f rcu: Make RCU_FAS... |
1495 |
return rcu_cpu_has_callbacks(cpu, NULL); |
7cb924990 rcu: Permit dynti... |
1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 |
} /* * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up * after it. */ static void rcu_cleanup_after_idle(int cpu) { } /* |
a858af287 rcu: Print schedu... |
1507 |
* Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n, |
aea1b35e2 rcu: Allow dyntic... |
1508 1509 1510 1511 1512 |
* is nothing. */ static void rcu_prepare_for_idle(int cpu) { } |
c57afe80d rcu: Make RCU_FAS... |
1513 1514 1515 1516 1517 1518 1519 |
/* * Don't bother keeping a running count of the number of RCU callbacks * posted because CONFIG_RCU_FAST_NO_HZ=n. */ static void rcu_idle_count_callbacks_posted(void) { } |
8bd93a2c5 rcu: Accelerate g... |
1520 |
#else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
f23f7fa1c rcu: Adaptive dyn... |
1521 1522 1523 1524 1525 1526 1527 1528 |
/* * This code is invoked when a CPU goes idle, at which point we want * to have the CPU do everything required for RCU so that it can enter * the energy-efficient dyntick-idle mode. This is handled by a * state machine implemented by rcu_prepare_for_idle() below. * * The following three proprocessor symbols control this state machine: * |
f23f7fa1c rcu: Adaptive dyn... |
1529 1530 1531 1532 1533 1534 1535 |
* RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted * to sleep in dyntick-idle mode with RCU callbacks pending. This * is sized to be roughly one RCU grace period. Those energy-efficiency * benchmarkers who might otherwise be tempted to set this to a large * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your * system. And if you are -that- concerned about energy efficiency, * just power the system down and be done with it! |
778d250a2 rcu: Limit lazy-c... |
1536 1537 1538 |
* RCU_IDLE_LAZY_GP_DELAY gives the number of jiffies that a CPU is * permitted to sleep in dyntick-idle mode with only lazy RCU * callbacks pending. Setting this too high can OOM your system. |
f23f7fa1c rcu: Adaptive dyn... |
1539 1540 1541 1542 1543 |
* * The values below work well in practice. If future workloads require * adjustment, they can be converted into kernel config parameters, though * making the state machine smarter might be a better option. */ |
e84c48ae3 rcu: Round FAST_N... |
1544 |
#define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */ |
778d250a2 rcu: Limit lazy-c... |
1545 |
#define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */ |
f23f7fa1c rcu: Adaptive dyn... |
1546 |
|
5e44ce35a rcu: Export RCU_F... |
1547 1548 1549 1550 |
static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY; module_param(rcu_idle_gp_delay, int, 0644); static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY; module_param(rcu_idle_lazy_gp_delay, int, 0644); |
486e25934 rcu: Avoid waking... |
1551 |
|
9d2ad2430 rcu: Make RCU_FAS... |
1552 |
extern int tick_nohz_enabled; |
486e25934 rcu: Avoid waking... |
1553 1554 |
/* |
c0f4dfd4f rcu: Make RCU_FAS... |
1555 1556 1557 |
* Try to advance callbacks for all flavors of RCU on the current CPU. * Afterwards, if there are any callbacks ready for immediate invocation, * return true. |
486e25934 rcu: Avoid waking... |
1558 |
*/ |
c0f4dfd4f rcu: Make RCU_FAS... |
1559 |
static bool rcu_try_advance_all_cbs(void) |
486e25934 rcu: Avoid waking... |
1560 |
{ |
c0f4dfd4f rcu: Make RCU_FAS... |
1561 1562 1563 1564 |
bool cbs_ready = false; struct rcu_data *rdp; struct rcu_node *rnp; struct rcu_state *rsp; |
486e25934 rcu: Avoid waking... |
1565 |
|
c0f4dfd4f rcu: Make RCU_FAS... |
1566 1567 1568 |
for_each_rcu_flavor(rsp) { rdp = this_cpu_ptr(rsp->rda); rnp = rdp->mynode; |
486e25934 rcu: Avoid waking... |
1569 |
|
c0f4dfd4f rcu: Make RCU_FAS... |
1570 1571 1572 1573 1574 1575 1576 1577 |
/* * Don't bother checking unless a grace period has * completed since we last checked and there are * callbacks not yet ready to invoke. */ if (rdp->completed != rnp->completed && rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL]) rcu_process_gp_end(rsp, rdp); |
486e25934 rcu: Avoid waking... |
1578 |
|
c0f4dfd4f rcu: Make RCU_FAS... |
1579 1580 1581 1582 |
if (cpu_has_callbacks_ready_to_invoke(rdp)) cbs_ready = true; } return cbs_ready; |
486e25934 rcu: Avoid waking... |
1583 1584 1585 |
} /* |
c0f4dfd4f rcu: Make RCU_FAS... |
1586 1587 1588 1589 |
* Allow the CPU to enter dyntick-idle mode unless it has callbacks ready * to invoke. If the CPU has callbacks, try to advance them. Tell the * caller to set the timeout based on whether or not there are non-lazy * callbacks. |
aa9b16306 rcu: Precompute R... |
1590 |
* |
c0f4dfd4f rcu: Make RCU_FAS... |
1591 |
* The caller must have disabled interrupts. |
aa9b16306 rcu: Precompute R... |
1592 |
*/ |
c0f4dfd4f rcu: Make RCU_FAS... |
1593 |
int rcu_needs_cpu(int cpu, unsigned long *dj) |
aa9b16306 rcu: Precompute R... |
1594 1595 |
{ struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
c0f4dfd4f rcu: Make RCU_FAS... |
1596 1597 |
/* Snapshot to detect later posting of non-lazy callback. */ rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; |
aa9b16306 rcu: Precompute R... |
1598 |
/* If no callbacks, RCU doesn't need the CPU. */ |
c0f4dfd4f rcu: Make RCU_FAS... |
1599 1600 |
if (!rcu_cpu_has_callbacks(cpu, &rdtp->all_lazy)) { *dj = ULONG_MAX; |
aa9b16306 rcu: Precompute R... |
1601 1602 |
return 0; } |
c0f4dfd4f rcu: Make RCU_FAS... |
1603 1604 1605 1606 1607 |
/* Attempt to advance callbacks. */ if (rcu_try_advance_all_cbs()) { /* Some ready to invoke, so initiate later invocation. */ invoke_rcu_core(); |
aa9b16306 rcu: Precompute R... |
1608 1609 |
return 1; } |
c0f4dfd4f rcu: Make RCU_FAS... |
1610 1611 1612 |
rdtp->last_accelerate = jiffies; /* Request timer delay depending on laziness, and round. */ |
6faf72834 rcu: Fix comparis... |
1613 |
if (!rdtp->all_lazy) { |
c0f4dfd4f rcu: Make RCU_FAS... |
1614 1615 |
*dj = round_up(rcu_idle_gp_delay + jiffies, rcu_idle_gp_delay) - jiffies; |
e84c48ae3 rcu: Round FAST_N... |
1616 |
} else { |
c0f4dfd4f rcu: Make RCU_FAS... |
1617 |
*dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies; |
e84c48ae3 rcu: Round FAST_N... |
1618 |
} |
aa9b16306 rcu: Precompute R... |
1619 1620 1621 1622 |
return 0; } /* |
c0f4dfd4f rcu: Make RCU_FAS... |
1623 1624 1625 1626 1627 1628 |
* Prepare a CPU for idle from an RCU perspective. The first major task * is to sense whether nohz mode has been enabled or disabled via sysfs. * The second major task is to check to see if a non-lazy callback has * arrived at a CPU that previously had only lazy callbacks. The third * major task is to accelerate (that is, assign grace-period numbers to) * any recently arrived callbacks. |
aea1b35e2 rcu: Allow dyntic... |
1629 1630 |
* * The caller must have disabled interrupts. |
8bd93a2c5 rcu: Accelerate g... |
1631 |
*/ |
aea1b35e2 rcu: Allow dyntic... |
1632 |
static void rcu_prepare_for_idle(int cpu) |
8bd93a2c5 rcu: Accelerate g... |
1633 |
{ |
c0f4dfd4f rcu: Make RCU_FAS... |
1634 |
struct rcu_data *rdp; |
5955f7eec rcu: Move RCU_FAS... |
1635 |
struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
c0f4dfd4f rcu: Make RCU_FAS... |
1636 1637 |
struct rcu_node *rnp; struct rcu_state *rsp; |
9d2ad2430 rcu: Make RCU_FAS... |
1638 1639 1640 1641 1642 |
int tne; /* Handle nohz enablement switches conservatively. */ tne = ACCESS_ONCE(tick_nohz_enabled); if (tne != rdtp->tick_nohz_enabled_snap) { |
c0f4dfd4f rcu: Make RCU_FAS... |
1643 |
if (rcu_cpu_has_callbacks(cpu, NULL)) |
9d2ad2430 rcu: Make RCU_FAS... |
1644 1645 1646 1647 1648 1649 |
invoke_rcu_core(); /* force nohz to see update. */ rdtp->tick_nohz_enabled_snap = tne; return; } if (!tne) return; |
f511fc624 rcu: Ensure that ... |
1650 |
|
c0f4dfd4f rcu: Make RCU_FAS... |
1651 |
/* If this is a no-CBs CPU, no callbacks, just return. */ |
534c97b09 Merge branch 'tim... |
1652 |
if (rcu_is_nocb_cpu(cpu)) |
9a0c6fef4 rcu: Make RCU_FAS... |
1653 |
return; |
9a0c6fef4 rcu: Make RCU_FAS... |
1654 |
|
3084f2f80 rcu: Go dyntick-i... |
1655 |
/* |
c0f4dfd4f rcu: Make RCU_FAS... |
1656 1657 1658 |
* If a non-lazy callback arrived at a CPU having only lazy * callbacks, invoke RCU core for the side-effect of recalculating * idle duration on re-entry to idle. |
c57afe80d rcu: Make RCU_FAS... |
1659 |
*/ |
c0f4dfd4f rcu: Make RCU_FAS... |
1660 1661 1662 |
if (rdtp->all_lazy && rdtp->nonlazy_posted != rdtp->nonlazy_posted_snap) { invoke_rcu_core(); |
c57afe80d rcu: Make RCU_FAS... |
1663 1664 |
return; } |
c57afe80d rcu: Make RCU_FAS... |
1665 1666 |
/* |
c0f4dfd4f rcu: Make RCU_FAS... |
1667 1668 |
* If we have not yet accelerated this jiffy, accelerate all * callbacks on this CPU. |
3084f2f80 rcu: Go dyntick-i... |
1669 |
*/ |
c0f4dfd4f rcu: Make RCU_FAS... |
1670 |
if (rdtp->last_accelerate == jiffies) |
aea1b35e2 rcu: Allow dyntic... |
1671 |
return; |
c0f4dfd4f rcu: Make RCU_FAS... |
1672 1673 1674 1675 1676 1677 1678 1679 1680 |
rdtp->last_accelerate = jiffies; for_each_rcu_flavor(rsp) { rdp = per_cpu_ptr(rsp->rda, cpu); if (!*rdp->nxttail[RCU_DONE_TAIL]) continue; rnp = rdp->mynode; raw_spin_lock(&rnp->lock); /* irqs already disabled. */ rcu_accelerate_cbs(rsp, rnp, rdp); raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
77e38ed34 rcu: RCU_FAST_NO_... |
1681 |
} |
c0f4dfd4f rcu: Make RCU_FAS... |
1682 |
} |
3084f2f80 rcu: Go dyntick-i... |
1683 |
|
c0f4dfd4f rcu: Make RCU_FAS... |
1684 1685 1686 1687 1688 1689 1690 1691 1692 |
/* * Clean up for exit from idle. Attempt to advance callbacks based on * any grace periods that elapsed while the CPU was idle, and if any * callbacks are now ready to invoke, initiate invocation. */ static void rcu_cleanup_after_idle(int cpu) { struct rcu_data *rdp; struct rcu_state *rsp; |
a47cd880b rcu: Fix accelera... |
1693 |
|
534c97b09 Merge branch 'tim... |
1694 |
if (rcu_is_nocb_cpu(cpu)) |
aea1b35e2 rcu: Allow dyntic... |
1695 |
return; |
c0f4dfd4f rcu: Make RCU_FAS... |
1696 1697 1698 1699 1700 |
rcu_try_advance_all_cbs(); for_each_rcu_flavor(rsp) { rdp = per_cpu_ptr(rsp->rda, cpu); if (cpu_has_callbacks_ready_to_invoke(rdp)) invoke_rcu_core(); |
c701d5d9b rcu: Fix code-sty... |
1701 |
} |
8bd93a2c5 rcu: Accelerate g... |
1702 |
} |
c57afe80d rcu: Make RCU_FAS... |
1703 |
/* |
98248a0e2 rcu: Explicitly i... |
1704 1705 1706 1707 1708 1709 |
* Keep a running count of the number of non-lazy callbacks posted * on this CPU. This running counter (which is never decremented) allows * rcu_prepare_for_idle() to detect when something out of the idle loop * posts a callback, even if an equal number of callbacks are invoked. * Of course, callbacks should only be posted from within a trace event * designed to be called from idle or from within RCU_NONIDLE(). |
c57afe80d rcu: Make RCU_FAS... |
1710 1711 1712 |
*/ static void rcu_idle_count_callbacks_posted(void) { |
5955f7eec rcu: Move RCU_FAS... |
1713 |
__this_cpu_add(rcu_dynticks.nonlazy_posted, 1); |
c57afe80d rcu: Make RCU_FAS... |
1714 |
} |
b626c1b68 rcu: Provide OOM ... |
1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 |
/* * Data for flushing lazy RCU callbacks at OOM time. */ static atomic_t oom_callback_count; static DECLARE_WAIT_QUEUE_HEAD(oom_callback_wq); /* * RCU OOM callback -- decrement the outstanding count and deliver the * wake-up if we are the last one. */ static void rcu_oom_callback(struct rcu_head *rhp) { if (atomic_dec_and_test(&oom_callback_count)) wake_up(&oom_callback_wq); } /* * Post an rcu_oom_notify callback on the current CPU if it has at * least one lazy callback. This will unnecessarily post callbacks * to CPUs that already have a non-lazy callback at the end of their * callback list, but this is an infrequent operation, so accept some * extra overhead to keep things simple. */ static void rcu_oom_notify_cpu(void *unused) { struct rcu_state *rsp; struct rcu_data *rdp; for_each_rcu_flavor(rsp) { rdp = __this_cpu_ptr(rsp->rda); if (rdp->qlen_lazy != 0) { atomic_inc(&oom_callback_count); rsp->call(&rdp->oom_head, rcu_oom_callback); } } } /* * If low on memory, ensure that each CPU has a non-lazy callback. * This will wake up CPUs that have only lazy callbacks, in turn * ensuring that they free up the corresponding memory in a timely manner. * Because an uncertain amount of memory will be freed in some uncertain * timeframe, we do not claim to have freed anything. */ static int rcu_oom_notify(struct notifier_block *self, unsigned long notused, void *nfreed) { int cpu; /* Wait for callbacks from earlier instance to complete. */ wait_event(oom_callback_wq, atomic_read(&oom_callback_count) == 0); /* * Prevent premature wakeup: ensure that all increments happen * before there is a chance of the counter reaching zero. */ atomic_set(&oom_callback_count, 1); get_online_cpus(); for_each_online_cpu(cpu) { smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1); cond_resched(); } put_online_cpus(); /* Unconditionally decrement: no need to wake ourselves up. */ atomic_dec(&oom_callback_count); return NOTIFY_OK; } static struct notifier_block rcu_oom_nb = { .notifier_call = rcu_oom_notify }; static int __init rcu_register_oom_notifier(void) { register_oom_notifier(&rcu_oom_nb); return 0; } early_initcall(rcu_register_oom_notifier); |
8bd93a2c5 rcu: Accelerate g... |
1796 |
#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
a858af287 rcu: Print schedu... |
1797 1798 1799 1800 1801 1802 1803 |
#ifdef CONFIG_RCU_CPU_STALL_INFO #ifdef CONFIG_RCU_FAST_NO_HZ static void print_cpu_stall_fast_no_hz(char *cp, int cpu) { |
5955f7eec rcu: Move RCU_FAS... |
1804 |
struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
c0f4dfd4f rcu: Make RCU_FAS... |
1805 |
unsigned long nlpd = rdtp->nonlazy_posted - rdtp->nonlazy_posted_snap; |
a858af287 rcu: Print schedu... |
1806 |
|
c0f4dfd4f rcu: Make RCU_FAS... |
1807 1808 1809 1810 1811 |
sprintf(cp, "last_accelerate: %04lx/%04lx, nonlazy_posted: %ld, %c%c", rdtp->last_accelerate & 0xffff, jiffies & 0xffff, ulong2long(nlpd), rdtp->all_lazy ? 'L' : '.', rdtp->tick_nohz_enabled_snap ? '.' : 'D'); |
a858af287 rcu: Print schedu... |
1812 1813 1814 1815 1816 1817 |
} #else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ static void print_cpu_stall_fast_no_hz(char *cp, int cpu) { |
1c17e4d44 rcu: Prevent unin... |
1818 |
*cp = '\0'; |
a858af287 rcu: Print schedu... |
1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 |
} #endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */ /* Initiate the stall-info list. */ static void print_cpu_stall_info_begin(void) { printk(KERN_CONT " "); } /* * Print out diagnostic information for the specified stalled CPU. * * If the specified CPU is aware of the current RCU grace period * (flavor specified by rsp), then print the number of scheduling * clock interrupts the CPU has taken during the time that it has * been aware. Otherwise, print the number of RCU grace periods * that this CPU is ignorant of, for example, "1" if the CPU was * aware of the previous grace period. * * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info. */ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) { char fast_no_hz[72]; struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); struct rcu_dynticks *rdtp = rdp->dynticks; char *ticks_title; unsigned long ticks_value; if (rsp->gpnum == rdp->gpnum) { ticks_title = "ticks this GP"; ticks_value = rdp->ticks_this_gp; } else { ticks_title = "GPs behind"; ticks_value = rsp->gpnum - rdp->gpnum; } print_cpu_stall_fast_no_hz(fast_no_hz, cpu); |
6231069bd rcu: Add softirq-... |
1858 1859 |
printk(KERN_ERR "\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u %s ", |
a858af287 rcu: Print schedu... |
1860 1861 1862 |
cpu, ticks_value, ticks_title, atomic_read(&rdtp->dynticks) & 0xfff, rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting, |
6231069bd rcu: Add softirq-... |
1863 |
rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu), |
a858af287 rcu: Print schedu... |
1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 |
fast_no_hz); } /* Terminate the stall-info list. */ static void print_cpu_stall_info_end(void) { printk(KERN_ERR "\t"); } /* Zero ->ticks_this_gp for all flavors of RCU. */ static void zero_cpu_stall_ticks(struct rcu_data *rdp) { rdp->ticks_this_gp = 0; |
6231069bd rcu: Add softirq-... |
1877 |
rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id()); |
a858af287 rcu: Print schedu... |
1878 1879 1880 1881 1882 |
} /* Increment ->ticks_this_gp for all flavors of RCU. */ static void increment_cpu_stall_ticks(void) { |
115f7a7ca rcu: Apply for_ea... |
1883 1884 1885 1886 |
struct rcu_state *rsp; for_each_rcu_flavor(rsp) __this_cpu_ptr(rsp->rda)->ticks_this_gp++; |
a858af287 rcu: Print schedu... |
1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 |
} #else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ static void print_cpu_stall_info_begin(void) { printk(KERN_CONT " {"); } static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) { printk(KERN_CONT " %d", cpu); } static void print_cpu_stall_info_end(void) { printk(KERN_CONT "} "); } static void zero_cpu_stall_ticks(struct rcu_data *rdp) { } static void increment_cpu_stall_ticks(void) { } #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ |
3fbfbf7a3 rcu: Add callback... |
1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 |
#ifdef CONFIG_RCU_NOCB_CPU /* * Offload callback processing from the boot-time-specified set of CPUs * specified by rcu_nocb_mask. For each CPU in the set, there is a * kthread created that pulls the callbacks from the corresponding CPU, * waits for a grace period to elapse, and invokes the callbacks. * The no-CBs CPUs do a wake_up() on their kthread when they insert * a callback into any empty list, unless the rcu_nocb_poll boot parameter * has been specified, in which case each kthread actively polls its * CPU. (Which isn't so great for energy efficiency, but which does * reduce RCU's overhead on that CPU.) * * This is intended to be used in conjunction with Frederic Weisbecker's * adaptive-idle work, which would seriously reduce OS jitter on CPUs * running CPU-bound user-mode computations. * * Offloading of callback processing could also in theory be used as * an energy-efficiency measure because CPUs with no RCU callbacks * queued are more aggressive about entering dyntick-idle mode. */ /* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. */ static int __init rcu_nocb_setup(char *str) { alloc_bootmem_cpumask_var(&rcu_nocb_mask); have_rcu_nocb_mask = true; cpulist_parse(str, rcu_nocb_mask); return 1; } __setup("rcu_nocbs=", rcu_nocb_setup); |
1b0048a44 rcu: Make rcu_noc... |
1948 1949 1950 1951 1952 1953 |
static int __init parse_rcu_nocb_poll(char *arg) { rcu_nocb_poll = 1; return 0; } early_param("rcu_nocb_poll", parse_rcu_nocb_poll); |
34ed62461 rcu: Remove restr... |
1954 |
/* |
dae6e64d2 rcu: Introduce pr... |
1955 1956 1957 1958 1959 1960 1961 1962 |
* Do any no-CBs CPUs need another grace period? * * Interrupts must be disabled. If the caller does not hold the root * rnp_node structure's ->lock, the results are advisory only. */ static int rcu_nocb_needs_gp(struct rcu_state *rsp) { struct rcu_node *rnp = rcu_get_root(rsp); |
8b425aa8f rcu: Rename n_noc... |
1963 |
return rnp->need_future_gp[(ACCESS_ONCE(rnp->completed) + 1) & 0x1]; |
dae6e64d2 rcu: Introduce pr... |
1964 1965 1966 |
} /* |
0446be489 rcu: Abstract rcu... |
1967 1968 |
* Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended * grace period. |
dae6e64d2 rcu: Introduce pr... |
1969 |
*/ |
0446be489 rcu: Abstract rcu... |
1970 |
static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) |
dae6e64d2 rcu: Introduce pr... |
1971 |
{ |
0446be489 rcu: Abstract rcu... |
1972 |
wake_up_all(&rnp->nocb_gp_wq[rnp->completed & 0x1]); |
dae6e64d2 rcu: Introduce pr... |
1973 1974 1975 |
} /* |
8b425aa8f rcu: Rename n_noc... |
1976 |
* Set the root rcu_node structure's ->need_future_gp field |
dae6e64d2 rcu: Introduce pr... |
1977 1978 1979 1980 1981 |
* based on the sum of those of all rcu_node structures. This does * double-count the root rcu_node structure's requests, but this * is necessary to handle the possibility of a rcu_nocb_kthread() * having awakened during the time that the rcu_node structures * were being updated for the end of the previous grace period. |
34ed62461 rcu: Remove restr... |
1982 |
*/ |
dae6e64d2 rcu: Introduce pr... |
1983 1984 |
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) { |
8b425aa8f rcu: Rename n_noc... |
1985 |
rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq; |
dae6e64d2 rcu: Introduce pr... |
1986 1987 1988 |
} static void rcu_init_one_nocb(struct rcu_node *rnp) |
34ed62461 rcu: Remove restr... |
1989 |
{ |
dae6e64d2 rcu: Introduce pr... |
1990 1991 |
init_waitqueue_head(&rnp->nocb_gp_wq[0]); init_waitqueue_head(&rnp->nocb_gp_wq[1]); |
34ed62461 rcu: Remove restr... |
1992 |
} |
3fbfbf7a3 rcu: Add callback... |
1993 |
/* Is the specified CPU a no-CPUs CPU? */ |
d1e43fa5f nohz: Ensure full... |
1994 |
bool rcu_is_nocb_cpu(int cpu) |
3fbfbf7a3 rcu: Add callback... |
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 |
{ if (have_rcu_nocb_mask) return cpumask_test_cpu(cpu, rcu_nocb_mask); return false; } /* * Enqueue the specified string of rcu_head structures onto the specified * CPU's no-CBs lists. The CPU is specified by rdp, the head of the * string by rhp, and the tail of the string by rhtp. The non-lazy/lazy * counts are supplied by rhcount and rhcount_lazy. * * If warranted, also wake up the kthread servicing this CPUs queues. */ static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, struct rcu_head *rhp, struct rcu_head **rhtp, int rhcount, int rhcount_lazy) { int len; struct rcu_head **old_rhpp; struct task_struct *t; /* Enqueue the callback on the nocb list and update counts. */ old_rhpp = xchg(&rdp->nocb_tail, rhtp); ACCESS_ONCE(*old_rhpp) = rhp; atomic_long_add(rhcount, &rdp->nocb_q_count); atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy); /* If we are not being polled and there is a kthread, awaken it ... */ t = ACCESS_ONCE(rdp->nocb_kthread); if (rcu_nocb_poll | !t) return; len = atomic_long_read(&rdp->nocb_q_count); if (old_rhpp == &rdp->nocb_head) { wake_up(&rdp->nocb_wq); /* ... only if queue was empty ... */ rdp->qlen_last_fqs_check = 0; } else if (len > rdp->qlen_last_fqs_check + qhimark) { wake_up_process(t); /* ... or if many callbacks queued. */ rdp->qlen_last_fqs_check = LONG_MAX / 2; } return; } /* * This is a helper for __call_rcu(), which invokes this when the normal * callback queue is inoperable. If this is not a no-CBs CPU, this * function returns failure back to __call_rcu(), which can complain * appropriately. * * Otherwise, this function queues the callback where the corresponding * "rcuo" kthread can find it. */ static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, bool lazy) { |
d1e43fa5f nohz: Ensure full... |
2051 |
if (!rcu_is_nocb_cpu(rdp->cpu)) |
3fbfbf7a3 rcu: Add callback... |
2052 2053 |
return 0; __call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy); |
21e7a6087 rcu: Add event tr... |
2054 2055 2056 2057 2058 2059 2060 |
if (__is_kfree_rcu_offset((unsigned long)rhp->func)) trace_rcu_kfree_callback(rdp->rsp->name, rhp, (unsigned long)rhp->func, rdp->qlen_lazy, rdp->qlen); else trace_rcu_callback(rdp->rsp->name, rhp, rdp->qlen_lazy, rdp->qlen); |
3fbfbf7a3 rcu: Add callback... |
2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 |
return 1; } /* * Adopt orphaned callbacks on a no-CBs CPU, or return 0 if this is * not a no-CBs CPU. */ static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, struct rcu_data *rdp) { long ql = rsp->qlen; long qll = rsp->qlen_lazy; /* If this is not a no-CBs CPU, tell the caller to do it the old way. */ |
d1e43fa5f nohz: Ensure full... |
2075 |
if (!rcu_is_nocb_cpu(smp_processor_id())) |
3fbfbf7a3 rcu: Add callback... |
2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 |
return 0; rsp->qlen = 0; rsp->qlen_lazy = 0; /* First, enqueue the donelist, if any. This preserves CB ordering. */ if (rsp->orphan_donelist != NULL) { __call_rcu_nocb_enqueue(rdp, rsp->orphan_donelist, rsp->orphan_donetail, ql, qll); ql = qll = 0; rsp->orphan_donelist = NULL; rsp->orphan_donetail = &rsp->orphan_donelist; } if (rsp->orphan_nxtlist != NULL) { __call_rcu_nocb_enqueue(rdp, rsp->orphan_nxtlist, rsp->orphan_nxttail, ql, qll); ql = qll = 0; rsp->orphan_nxtlist = NULL; rsp->orphan_nxttail = &rsp->orphan_nxtlist; } return 1; } /* |
34ed62461 rcu: Remove restr... |
2099 2100 |
* If necessary, kick off a new grace period, and either way wait * for a subsequent grace period to complete. |
3fbfbf7a3 rcu: Add callback... |
2101 |
*/ |
34ed62461 rcu: Remove restr... |
2102 |
static void rcu_nocb_wait_gp(struct rcu_data *rdp) |
3fbfbf7a3 rcu: Add callback... |
2103 |
{ |
34ed62461 rcu: Remove restr... |
2104 |
unsigned long c; |
dae6e64d2 rcu: Introduce pr... |
2105 |
bool d; |
34ed62461 rcu: Remove restr... |
2106 |
unsigned long flags; |
34ed62461 rcu: Remove restr... |
2107 2108 2109 |
struct rcu_node *rnp = rdp->mynode; raw_spin_lock_irqsave(&rnp->lock, flags); |
0446be489 rcu: Abstract rcu... |
2110 2111 |
c = rcu_start_future_gp(rnp, rdp); raw_spin_unlock_irqrestore(&rnp->lock, flags); |
3fbfbf7a3 rcu: Add callback... |
2112 2113 |
/* |
34ed62461 rcu: Remove restr... |
2114 2115 |
* Wait for the grace period. Do so interruptibly to avoid messing * up the load average. |
3fbfbf7a3 rcu: Add callback... |
2116 |
*/ |
0446be489 rcu: Abstract rcu... |
2117 |
trace_rcu_future_gp(rnp, rdp, c, "StartWait"); |
34ed62461 rcu: Remove restr... |
2118 |
for (;;) { |
dae6e64d2 rcu: Introduce pr... |
2119 2120 2121 2122 |
wait_event_interruptible( rnp->nocb_gp_wq[c & 0x1], (d = ULONG_CMP_GE(ACCESS_ONCE(rnp->completed), c))); if (likely(d)) |
34ed62461 rcu: Remove restr... |
2123 |
break; |
dae6e64d2 rcu: Introduce pr... |
2124 |
flush_signals(current); |
0446be489 rcu: Abstract rcu... |
2125 |
trace_rcu_future_gp(rnp, rdp, c, "ResumeWait"); |
34ed62461 rcu: Remove restr... |
2126 |
} |
0446be489 rcu: Abstract rcu... |
2127 |
trace_rcu_future_gp(rnp, rdp, c, "EndWait"); |
34ed62461 rcu: Remove restr... |
2128 |
smp_mb(); /* Ensure that CB invocation happens after GP end. */ |
3fbfbf7a3 rcu: Add callback... |
2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 |
} /* * Per-rcu_data kthread, but only for no-CBs CPUs. Each kthread invokes * callbacks queued by the corresponding no-CBs CPU. */ static int rcu_nocb_kthread(void *arg) { int c, cl; struct rcu_head *list; struct rcu_head *next; struct rcu_head **tail; struct rcu_data *rdp = arg; /* Each pass through this loop invokes one batch of callbacks */ for (;;) { /* If not polling, wait for next batch of callbacks. */ if (!rcu_nocb_poll) |
353af9c9a rcu: Prevent soft... |
2147 |
wait_event_interruptible(rdp->nocb_wq, rdp->nocb_head); |
3fbfbf7a3 rcu: Add callback... |
2148 2149 2150 |
list = ACCESS_ONCE(rdp->nocb_head); if (!list) { schedule_timeout_interruptible(1); |
353af9c9a rcu: Prevent soft... |
2151 |
flush_signals(current); |
3fbfbf7a3 rcu: Add callback... |
2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 |
continue; } /* * Extract queued callbacks, update counts, and wait * for a grace period to elapse. */ ACCESS_ONCE(rdp->nocb_head) = NULL; tail = xchg(&rdp->nocb_tail, &rdp->nocb_head); c = atomic_long_xchg(&rdp->nocb_q_count, 0); cl = atomic_long_xchg(&rdp->nocb_q_count_lazy, 0); ACCESS_ONCE(rdp->nocb_p_count) += c; ACCESS_ONCE(rdp->nocb_p_count_lazy) += cl; |
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rcu_nocb_wait_gp(rdp); |
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/* Each pass through the following loop invokes a callback. */ trace_rcu_batch_start(rdp->rsp->name, cl, c, -1); c = cl = 0; while (list) { next = list->next; /* Wait for enqueuing to complete, if needed. */ while (next == NULL && &list->next != tail) { schedule_timeout_interruptible(1); next = list->next; } debug_rcu_head_unqueue(list); local_bh_disable(); if (__rcu_reclaim(rdp->rsp->name, list)) cl++; c++; local_bh_enable(); list = next; } trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1); ACCESS_ONCE(rdp->nocb_p_count) -= c; ACCESS_ONCE(rdp->nocb_p_count_lazy) -= cl; |
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rdp->n_nocbs_invoked += c; |
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} return 0; } /* Initialize per-rcu_data variables for no-CBs CPUs. */ static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) { rdp->nocb_tail = &rdp->nocb_head; init_waitqueue_head(&rdp->nocb_wq); } /* Create a kthread for each RCU flavor for each no-CBs CPU. */ static void __init rcu_spawn_nocb_kthreads(struct rcu_state *rsp) { int cpu; struct rcu_data *rdp; struct task_struct *t; if (rcu_nocb_mask == NULL) return; for_each_cpu(cpu, rcu_nocb_mask) { rdp = per_cpu_ptr(rsp->rda, cpu); |
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t = kthread_run(rcu_nocb_kthread, rdp, "rcuo%c/%d", rsp->abbr, cpu); |
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BUG_ON(IS_ERR(t)); ACCESS_ONCE(rdp->nocb_kthread) = t; } } /* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ |
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static bool init_nocb_callback_list(struct rcu_data *rdp) |
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{ if (rcu_nocb_mask == NULL || !cpumask_test_cpu(rdp->cpu, rcu_nocb_mask)) |
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return false; |
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rdp->nxttail[RCU_NEXT_TAIL] = NULL; |
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return true; |
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} |
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#else /* #ifdef CONFIG_RCU_NOCB_CPU */ |
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static int rcu_nocb_needs_gp(struct rcu_state *rsp) { return 0; |
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} |
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static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) |
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{ |
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} |
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static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) { } static void rcu_init_one_nocb(struct rcu_node *rnp) { } |
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|
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static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, bool lazy) { return 0; } static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, struct rcu_data *rdp) { return 0; } |
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static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) { } static void __init rcu_spawn_nocb_kthreads(struct rcu_state *rsp) { } |
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static bool init_nocb_callback_list(struct rcu_data *rdp) |
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{ |
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return false; |
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} #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ |
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/* * An adaptive-ticks CPU can potentially execute in kernel mode for an * arbitrarily long period of time with the scheduling-clock tick turned * off. RCU will be paying attention to this CPU because it is in the * kernel, but the CPU cannot be guaranteed to be executing the RCU state * machine because the scheduling-clock tick has been disabled. Therefore, * if an adaptive-ticks CPU is failing to respond to the current grace * period and has not be idle from an RCU perspective, kick it. */ static void rcu_kick_nohz_cpu(int cpu) { #ifdef CONFIG_NO_HZ_FULL if (tick_nohz_full_cpu(cpu)) smp_send_reschedule(cpu); #endif /* #ifdef CONFIG_NO_HZ_FULL */ } |