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kernel/rcutree_plugin.h
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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/stop_machine.h> |
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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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/* * 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 "\tVerbose stalled-CPUs detection is disabled. "); #endif #if NUM_RCU_LVL_4 != 0 printk(KERN_INFO "\tExperimental four-level hierarchy is enabled. "); #endif } |
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#ifdef CONFIG_TREE_PREEMPT_RCU |
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struct rcu_state rcu_preempt_state = RCU_STATE_INITIALIZER(rcu_preempt); |
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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 void rcu_read_unlock_special(struct task_struct *t); |
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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) { force_quiescent_state(&rcu_preempt_state, 0); } 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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rdp->passed_quiesce_gpnum = rdp->gpnum; |
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barrier(); |
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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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* Tree-preemptible RCU implementation for rcu_read_lock(). |
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* Just increment ->rcu_read_lock_nesting, shared state will be updated * if we block. */ void __rcu_read_lock(void) { |
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current->rcu_read_lock_nesting++; |
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barrier(); /* needed if we ever invoke rcu_read_lock in rcutree.c */ } EXPORT_SYMBOL_GPL(__rcu_read_lock); |
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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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static noinline 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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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. |
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*/ |
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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 raw_spin_unlock_irqrestore(&rnp->lock, flags); |
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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); |
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#endif /* #ifdef CONFIG_RCU_BOOST */ |
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/* * If this was the last task on the expedited lists, * then we need to report up the rcu_node hierarchy. */ if (!empty_exp && !rcu_preempted_readers_exp(rnp)) rcu_report_exp_rnp(&rcu_preempt_state, rnp); |
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} else { local_irq_restore(flags); |
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} |
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} /* |
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* Tree-preemptible RCU implementation for rcu_read_unlock(). |
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* Decrement ->rcu_read_lock_nesting. If the result is zero (outermost * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then * invoke rcu_read_unlock_special() to clean up after a context switch * in an RCU read-side critical section and other special cases. */ void __rcu_read_unlock(void) { struct task_struct *t = current; |
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if (t->rcu_read_lock_nesting != 1) --t->rcu_read_lock_nesting; else { |
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barrier(); /* critical section before exit code. */ |
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t->rcu_read_lock_nesting = INT_MIN; barrier(); /* assign before ->rcu_read_unlock_special load */ |
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if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) rcu_read_unlock_special(t); |
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barrier(); /* ->rcu_read_unlock_special load before assign */ t->rcu_read_lock_nesting = 0; |
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} |
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#ifdef CONFIG_PROVE_LOCKING |
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{ int rrln = ACCESS_ONCE(t->rcu_read_lock_nesting); WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2); } |
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#endif /* #ifdef CONFIG_PROVE_LOCKING */ |
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} EXPORT_SYMBOL_GPL(__rcu_read_unlock); |
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#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; |
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453 |
struct task_struct *t; |
27f4d2805 rcu: priority boo... |
454 |
if (!rcu_preempt_blocked_readers_cgp(rnp)) |
12f5f524c rcu: merge TREE_P... |
455 456 457 458 459 460 461 |
return; raw_spin_lock_irqsave(&rnp->lock, flags); 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_... |
462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 |
} /* * 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 */ |
f41d911f8 rcu: Merge preemp... |
484 485 486 487 |
/* * Scan the current list of tasks blocked within RCU read-side critical * sections, printing out the tid of each. */ |
9bc8b5586 rcu: Suppress NMI... |
488 |
static int rcu_print_task_stall(struct rcu_node *rnp) |
f41d911f8 rcu: Merge preemp... |
489 |
{ |
f41d911f8 rcu: Merge preemp... |
490 |
struct task_struct *t; |
9bc8b5586 rcu: Suppress NMI... |
491 |
int ndetected = 0; |
f41d911f8 rcu: Merge preemp... |
492 |
|
27f4d2805 rcu: priority boo... |
493 |
if (!rcu_preempt_blocked_readers_cgp(rnp)) |
9bc8b5586 rcu: Suppress NMI... |
494 |
return 0; |
12f5f524c rcu: merge TREE_P... |
495 496 |
t = list_entry(rnp->gp_tasks, struct task_struct, rcu_node_entry); |
9bc8b5586 rcu: Suppress NMI... |
497 |
list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { |
12f5f524c rcu: merge TREE_P... |
498 |
printk(" P%d", t->pid); |
9bc8b5586 rcu: Suppress NMI... |
499 500 501 |
ndetected++; } return ndetected; |
f41d911f8 rcu: Merge preemp... |
502 |
} |
53d84e004 rcu: permit suppr... |
503 504 505 506 507 508 509 510 511 |
/* * Suppress preemptible RCU's CPU stall warnings by pushing the * time of the next stall-warning message comfortably far into the * future. */ static void rcu_preempt_stall_reset(void) { rcu_preempt_state.jiffies_stall = jiffies + ULONG_MAX / 2; } |
f41d911f8 rcu: Merge preemp... |
512 |
/* |
b0e165c03 rcu: Add debug ch... |
513 514 515 516 517 |
* 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... |
518 519 520 |
* * 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... |
521 522 523 |
*/ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) { |
27f4d2805 rcu: priority boo... |
524 |
WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); |
12f5f524c rcu: merge TREE_P... |
525 526 |
if (!list_empty(&rnp->blkd_tasks)) rnp->gp_tasks = rnp->blkd_tasks.next; |
28ecd5802 rcu: Add WARN_ON_... |
527 |
WARN_ON_ONCE(rnp->qsmask); |
b0e165c03 rcu: Add debug ch... |
528 |
} |
33f76148c rcu: Add CPU-offl... |
529 530 531 |
#ifdef CONFIG_HOTPLUG_CPU /* |
dd5d19baf rcu: Create rcutr... |
532 533 534 535 536 |
* 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... |
537 538 |
* Returns true if there were tasks blocking the current RCU grace * period. |
dd5d19baf rcu: Create rcutr... |
539 |
* |
237c80c5c rcu: Fix TREE_PRE... |
540 541 542 |
* Returns 1 if there was previously a task blocking the current grace * period on the specified rcu_node structure. * |
dd5d19baf rcu: Create rcutr... |
543 544 |
* The caller must hold rnp->lock with irqs disabled. */ |
237c80c5c rcu: Fix TREE_PRE... |
545 546 547 |
static int rcu_preempt_offline_tasks(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
dd5d19baf rcu: Create rcutr... |
548 |
{ |
dd5d19baf rcu: Create rcutr... |
549 550 |
struct list_head *lp; struct list_head *lp_root; |
d9a3da069 rcu: Add expedite... |
551 |
int retval = 0; |
dd5d19baf rcu: Create rcutr... |
552 |
struct rcu_node *rnp_root = rcu_get_root(rsp); |
12f5f524c rcu: merge TREE_P... |
553 |
struct task_struct *t; |
dd5d19baf rcu: Create rcutr... |
554 |
|
868489660 rcu: Changes from... |
555 556 |
if (rnp == rnp_root) { WARN_ONCE(1, "Last CPU thought to be offlined?"); |
237c80c5c rcu: Fix TREE_PRE... |
557 |
return 0; /* Shouldn't happen: at least one CPU online. */ |
868489660 rcu: Changes from... |
558 |
} |
12f5f524c rcu: merge TREE_P... |
559 560 561 |
/* If we are on an internal node, complain bitterly. */ WARN_ON_ONCE(rnp != rdp->mynode); |
dd5d19baf rcu: Create rcutr... |
562 563 |
/* |
12f5f524c rcu: merge TREE_P... |
564 565 566 567 568 569 570 |
* 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... |
571 |
*/ |
27f4d2805 rcu: priority boo... |
572 |
if (rcu_preempt_blocked_readers_cgp(rnp)) |
d9a3da069 rcu: Add expedite... |
573 574 575 |
retval |= RCU_OFL_TASKS_NORM_GP; if (rcu_preempted_readers_exp(rnp)) retval |= RCU_OFL_TASKS_EXP_GP; |
12f5f524c rcu: merge TREE_P... |
576 577 578 579 580 581 582 583 584 585 586 587 |
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... |
588 589 590 591 |
#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... |
592 |
raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */ |
dd5d19baf rcu: Create rcutr... |
593 |
} |
27f4d2805 rcu: priority boo... |
594 595 596 597 598 599 600 601 602 |
#ifdef CONFIG_RCU_BOOST /* In case root is being boosted and leaf is not. */ raw_spin_lock(&rnp_root->lock); /* irqs already disabled */ if (rnp_root->boost_tasks != NULL && rnp_root->boost_tasks != rnp_root->gp_tasks) rnp_root->boost_tasks = rnp_root->gp_tasks; raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */ #endif /* #ifdef CONFIG_RCU_BOOST */ |
12f5f524c rcu: merge TREE_P... |
603 604 |
rnp->gp_tasks = NULL; rnp->exp_tasks = NULL; |
237c80c5c rcu: Fix TREE_PRE... |
605 |
return retval; |
dd5d19baf rcu: Create rcutr... |
606 607 608 |
} /* |
6cc68793e rcu: fix spelling |
609 |
* Do CPU-offline processing for preemptible RCU. |
33f76148c rcu: Add CPU-offl... |
610 611 612 613 614 615 616 |
*/ static void rcu_preempt_offline_cpu(int cpu) { __rcu_offline_cpu(cpu, &rcu_preempt_state); } #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
f41d911f8 rcu: Merge preemp... |
617 618 619 620 621 622 623 624 625 626 627 628 |
/* * 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... |
629 |
rcu_preempt_qs(cpu); |
f41d911f8 rcu: Merge preemp... |
630 631 |
return; } |
10f39bb1b rcu: protect __rc... |
632 633 |
if (t->rcu_read_lock_nesting > 0 && per_cpu(rcu_preempt_data, cpu).qs_pending) |
c3422bea5 rcu: Simplify rcu... |
634 |
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; |
f41d911f8 rcu: Merge preemp... |
635 636 637 |
} /* |
6cc68793e rcu: fix spelling |
638 |
* Process callbacks for preemptible RCU. |
f41d911f8 rcu: Merge preemp... |
639 640 641 642 643 644 |
*/ static void rcu_preempt_process_callbacks(void) { __rcu_process_callbacks(&rcu_preempt_state, &__get_cpu_var(rcu_preempt_data)); } |
a46e0899e rcu: use softirq ... |
645 |
#ifdef CONFIG_RCU_BOOST |
09223371d rcu: Use softirq ... |
646 647 648 649 |
static void rcu_preempt_do_callbacks(void) { rcu_do_batch(&rcu_preempt_state, &__get_cpu_var(rcu_preempt_data)); } |
a46e0899e rcu: use softirq ... |
650 |
#endif /* #ifdef CONFIG_RCU_BOOST */ |
f41d911f8 rcu: Merge preemp... |
651 |
/* |
6cc68793e rcu: fix spelling |
652 |
* Queue a preemptible-RCU callback for invocation after a grace period. |
f41d911f8 rcu: Merge preemp... |
653 654 655 656 657 658 |
*/ void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) { __call_rcu(head, func, &rcu_preempt_state); } EXPORT_SYMBOL_GPL(call_rcu); |
6ebb237be rcu: Re-arrange c... |
659 660 661 662 663 |
/** * 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... |
664 665 666 667 668 |
* 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. |
6ebb237be rcu: Re-arrange c... |
669 670 671 |
*/ void synchronize_rcu(void) { |
6ebb237be rcu: Re-arrange c... |
672 673 |
if (!rcu_scheduler_active) return; |
2c42818e9 rcu: Abstract com... |
674 |
wait_rcu_gp(call_rcu); |
6ebb237be rcu: Re-arrange c... |
675 676 |
} EXPORT_SYMBOL_GPL(synchronize_rcu); |
d9a3da069 rcu: Add expedite... |
677 678 679 680 681 682 683 684 685 686 687 688 |
static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq); static long sync_rcu_preempt_exp_count; 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... |
689 |
return rnp->exp_tasks != NULL; |
d9a3da069 rcu: Add expedite... |
690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 |
} /* * 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!) * * Caller must hold sync_rcu_preempt_exp_mutex. */ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp) { unsigned long flags; unsigned long mask; |
1304afb22 rcu: Convert to r... |
721 |
raw_spin_lock_irqsave(&rnp->lock, flags); |
d9a3da069 rcu: Add expedite... |
722 |
for (;;) { |
131906b00 rcu: decrease rcu... |
723 724 |
if (!sync_rcu_preempt_exp_done(rnp)) { raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d9a3da069 rcu: Add expedite... |
725 |
break; |
131906b00 rcu: decrease rcu... |
726 |
} |
d9a3da069 rcu: Add expedite... |
727 |
if (rnp->parent == NULL) { |
131906b00 rcu: decrease rcu... |
728 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); |
d9a3da069 rcu: Add expedite... |
729 730 731 732 |
wake_up(&sync_rcu_preempt_exp_wq); break; } mask = rnp->grpmask; |
1304afb22 rcu: Convert to r... |
733 |
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
d9a3da069 rcu: Add expedite... |
734 |
rnp = rnp->parent; |
1304afb22 rcu: Convert to r... |
735 |
raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
d9a3da069 rcu: Add expedite... |
736 737 |
rnp->expmask &= ~mask; } |
d9a3da069 rcu: Add expedite... |
738 739 740 741 742 743 744 745 746 747 748 749 |
} /* * 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. * * Caller must hold sync_rcu_preempt_exp_mutex and rsp->onofflock. */ static void sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp) { |
1217ed1ba rcu: permit rcu_r... |
750 |
unsigned long flags; |
12f5f524c rcu: merge TREE_P... |
751 |
int must_wait = 0; |
d9a3da069 rcu: Add expedite... |
752 |
|
1217ed1ba rcu: permit rcu_r... |
753 754 755 756 |
raw_spin_lock_irqsave(&rnp->lock, flags); if (list_empty(&rnp->blkd_tasks)) raw_spin_unlock_irqrestore(&rnp->lock, flags); else { |
12f5f524c rcu: merge TREE_P... |
757 |
rnp->exp_tasks = rnp->blkd_tasks.next; |
1217ed1ba rcu: permit rcu_r... |
758 |
rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
12f5f524c rcu: merge TREE_P... |
759 760 |
must_wait = 1; } |
d9a3da069 rcu: Add expedite... |
761 762 763 |
if (!must_wait) rcu_report_exp_rnp(rsp, rnp); } |
f41d911f8 rcu: Merge preemp... |
764 |
/* |
d9a3da069 rcu: Add expedite... |
765 766 |
* 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 |
12f5f524c rcu: merge TREE_P... |
767 |
* the ->blkd_tasks lists and wait for this list to drain. |
019129d59 rcu: Stopgap fix ... |
768 769 770 |
*/ void synchronize_rcu_expedited(void) { |
d9a3da069 rcu: Add expedite... |
771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 |
unsigned long flags; struct rcu_node *rnp; struct rcu_state *rsp = &rcu_preempt_state; long snap; 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. */ /* * 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)) { if (trycount++ < 10) udelay(trycount * num_online_cpus()); else { synchronize_rcu(); return; } if ((ACCESS_ONCE(sync_rcu_preempt_exp_count) - snap) > 0) goto mb_ret; /* Others did our work for us. */ } if ((ACCESS_ONCE(sync_rcu_preempt_exp_count) - snap) > 0) goto unlock_mb_ret; /* Others did our work for us. */ |
12f5f524c rcu: merge TREE_P... |
798 |
/* force all RCU readers onto ->blkd_tasks lists. */ |
d9a3da069 rcu: Add expedite... |
799 |
synchronize_sched_expedited(); |
1304afb22 rcu: Convert to r... |
800 |
raw_spin_lock_irqsave(&rsp->onofflock, flags); |
d9a3da069 rcu: Add expedite... |
801 802 803 |
/* Initialize ->expmask for all non-leaf rcu_node structures. */ rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) { |
1304afb22 rcu: Convert to r... |
804 |
raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
d9a3da069 rcu: Add expedite... |
805 |
rnp->expmask = rnp->qsmaskinit; |
1304afb22 rcu: Convert to r... |
806 |
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
d9a3da069 rcu: Add expedite... |
807 |
} |
12f5f524c rcu: merge TREE_P... |
808 |
/* Snapshot current state of ->blkd_tasks lists. */ |
d9a3da069 rcu: Add expedite... |
809 810 811 812 |
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)); |
1304afb22 rcu: Convert to r... |
813 |
raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
d9a3da069 rcu: Add expedite... |
814 |
|
12f5f524c rcu: merge TREE_P... |
815 |
/* Wait for snapshotted ->blkd_tasks lists to drain. */ |
d9a3da069 rcu: Add expedite... |
816 817 818 819 820 821 822 823 824 825 826 |
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 ... |
827 828 829 830 |
} EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); /* |
6cc68793e rcu: fix spelling |
831 |
* Check to see if there is any immediate preemptible-RCU-related work |
f41d911f8 rcu: Merge preemp... |
832 833 834 835 836 837 838 839 840 |
* to be done. */ static int rcu_preempt_pending(int cpu) { return __rcu_pending(&rcu_preempt_state, &per_cpu(rcu_preempt_data, cpu)); } /* |
6cc68793e rcu: fix spelling |
841 |
* Does preemptible RCU need the CPU to stay out of dynticks mode? |
f41d911f8 rcu: Merge preemp... |
842 843 844 845 846 |
*/ static int rcu_preempt_needs_cpu(int cpu) { return !!per_cpu(rcu_preempt_data, cpu).nxtlist; } |
e74f4c456 rcu: Make hot-unp... |
847 848 849 850 851 852 853 854 |
/** * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. */ void rcu_barrier(void) { _rcu_barrier(&rcu_preempt_state, call_rcu); } EXPORT_SYMBOL_GPL(rcu_barrier); |
f41d911f8 rcu: Merge preemp... |
855 |
/* |
6cc68793e rcu: fix spelling |
856 |
* Initialize preemptible RCU's per-CPU data. |
f41d911f8 rcu: Merge preemp... |
857 858 859 860 861 862 863 |
*/ static void __cpuinit rcu_preempt_init_percpu_data(int cpu) { rcu_init_percpu_data(cpu, &rcu_preempt_state, 1); } /* |
6cc68793e rcu: fix spelling |
864 |
* Move preemptible RCU's callbacks from dying CPU to other online CPU. |
e74f4c456 rcu: Make hot-unp... |
865 |
*/ |
29494be71 rcu,cleanup: simp... |
866 |
static void rcu_preempt_send_cbs_to_online(void) |
e74f4c456 rcu: Make hot-unp... |
867 |
{ |
29494be71 rcu,cleanup: simp... |
868 |
rcu_send_cbs_to_online(&rcu_preempt_state); |
e74f4c456 rcu: Make hot-unp... |
869 870 871 |
} /* |
6cc68793e rcu: fix spelling |
872 |
* Initialize preemptible RCU's state structures. |
1eba8f843 rcu: Clean up cod... |
873 874 875 |
*/ static void __init __rcu_init_preempt(void) { |
394f99a90 rcu: simplify the... |
876 |
rcu_init_one(&rcu_preempt_state, &rcu_preempt_data); |
1eba8f843 rcu: Clean up cod... |
877 878 879 |
} /* |
6cc68793e rcu: fix spelling |
880 |
* Check for a task exiting while in a preemptible-RCU read-side |
f41d911f8 rcu: Merge preemp... |
881 882 883 884 885 886 887 888 889 890 891 |
* critical section, clean up if so. No need to issue warnings, * as debug_check_no_locks_held() already does this if lockdep * is enabled. */ void exit_rcu(void) { struct task_struct *t = current; if (t->rcu_read_lock_nesting == 0) return; t->rcu_read_lock_nesting = 1; |
13491a0ee rcu: call __rcu_r... |
892 |
__rcu_read_unlock(); |
f41d911f8 rcu: Merge preemp... |
893 894 895 |
} #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ |
27f4d2805 rcu: priority boo... |
896 |
static struct rcu_state *rcu_state = &rcu_sched_state; |
f41d911f8 rcu: Merge preemp... |
897 898 899 |
/* * Tell them what RCU they are running. */ |
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900 |
static void __init rcu_bootup_announce(void) |
f41d911f8 rcu: Merge preemp... |
901 902 903 |
{ printk(KERN_INFO "Hierarchical RCU implementation. "); |
26845c286 rcu: print boot-t... |
904 |
rcu_bootup_announce_oddness(); |
f41d911f8 rcu: Merge preemp... |
905 906 907 908 909 910 911 912 913 914 915 916 |
} /* * 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... |
917 918 919 920 921 922 923 924 925 926 |
* 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); /* |
6cc68793e rcu: fix spelling |
927 |
* Because preemptible RCU does not exist, we never have to check for |
f41d911f8 rcu: Merge preemp... |
928 929 |
* CPUs being in quiescent states. */ |
c3422bea5 rcu: Simplify rcu... |
930 |
static void rcu_preempt_note_context_switch(int cpu) |
f41d911f8 rcu: Merge preemp... |
931 932 |
{ } |
fc2219d49 rcu: Clean up cod... |
933 |
/* |
6cc68793e rcu: fix spelling |
934 |
* Because preemptible RCU does not exist, there are never any preempted |
fc2219d49 rcu: Clean up cod... |
935 936 |
* RCU readers. */ |
27f4d2805 rcu: priority boo... |
937 |
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
fc2219d49 rcu: Clean up cod... |
938 939 940 |
{ return 0; } |
b668c9cf3 rcu: Fix grace-pe... |
941 942 943 |
#ifdef CONFIG_HOTPLUG_CPU /* Because preemptible RCU does not exist, no quieting of tasks. */ |
d3f6bad39 rcu: Rename "quie... |
944 |
static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) |
b668c9cf3 rcu: Fix grace-pe... |
945 |
{ |
1304afb22 rcu: Convert to r... |
946 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); |
b668c9cf3 rcu: Fix grace-pe... |
947 948 949 |
} #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
f41d911f8 rcu: Merge preemp... |
950 |
/* |
6cc68793e rcu: fix spelling |
951 |
* Because preemptible RCU does not exist, we never have to check for |
f41d911f8 rcu: Merge preemp... |
952 953 |
* tasks blocked within RCU read-side critical sections. */ |
1ed509a22 rcu: Add RCU_CPU_... |
954 955 956 957 958 |
static void rcu_print_detail_task_stall(struct rcu_state *rsp) { } /* |
6cc68793e rcu: fix spelling |
959 |
* Because preemptible RCU does not exist, we never have to check for |
1ed509a22 rcu: Add RCU_CPU_... |
960 961 |
* tasks blocked within RCU read-side critical sections. */ |
9bc8b5586 rcu: Suppress NMI... |
962 |
static int rcu_print_task_stall(struct rcu_node *rnp) |
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963 |
{ |
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964 |
return 0; |
f41d911f8 rcu: Merge preemp... |
965 |
} |
53d84e004 rcu: permit suppr... |
966 967 968 969 970 971 972 |
/* * Because preemptible RCU does not exist, there is no need to suppress * its CPU stall warnings. */ static void rcu_preempt_stall_reset(void) { } |
f41d911f8 rcu: Merge preemp... |
973 |
/* |
6cc68793e rcu: fix spelling |
974 |
* Because there is no preemptible RCU, there can be no readers blocked, |
49e291266 rcu: Fix thinko, ... |
975 976 |
* so there is no need to check for blocked tasks. So check only for * bogus qsmask values. |
b0e165c03 rcu: Add debug ch... |
977 978 979 |
*/ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) { |
49e291266 rcu: Fix thinko, ... |
980 |
WARN_ON_ONCE(rnp->qsmask); |
b0e165c03 rcu: Add debug ch... |
981 |
} |
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982 983 984 |
#ifdef CONFIG_HOTPLUG_CPU /* |
6cc68793e rcu: fix spelling |
985 |
* Because preemptible RCU does not exist, it never needs to migrate |
237c80c5c rcu: Fix TREE_PRE... |
986 987 988 |
* 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... |
989 |
*/ |
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990 991 992 |
static int rcu_preempt_offline_tasks(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
dd5d19baf rcu: Create rcutr... |
993 |
{ |
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994 |
return 0; |
dd5d19baf rcu: Create rcutr... |
995 996 997 |
} /* |
6cc68793e rcu: fix spelling |
998 |
* Because preemptible RCU does not exist, it never needs CPU-offline |
33f76148c rcu: Add CPU-offl... |
999 1000 1001 1002 1003 1004 1005 |
* processing. */ static void rcu_preempt_offline_cpu(int cpu) { } #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
f41d911f8 rcu: Merge preemp... |
1006 |
/* |
6cc68793e rcu: fix spelling |
1007 |
* Because preemptible RCU does not exist, it never has any callbacks |
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1008 1009 |
* to check. */ |
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1010 |
static void rcu_preempt_check_callbacks(int cpu) |
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1011 1012 1013 1014 |
{ } /* |
6cc68793e rcu: fix spelling |
1015 |
* Because preemptible RCU does not exist, it never has any callbacks |
f41d911f8 rcu: Merge preemp... |
1016 1017 |
* to process. */ |
1eba8f843 rcu: Clean up cod... |
1018 |
static void rcu_preempt_process_callbacks(void) |
f41d911f8 rcu: Merge preemp... |
1019 1020 1021 1022 |
{ } /* |
019129d59 rcu: Stopgap fix ... |
1023 |
* Wait for an rcu-preempt grace period, but make it happen quickly. |
6cc68793e rcu: fix spelling |
1024 |
* But because preemptible RCU does not exist, map to rcu-sched. |
019129d59 rcu: Stopgap fix ... |
1025 1026 1027 1028 1029 1030 |
*/ void synchronize_rcu_expedited(void) { synchronize_sched_expedited(); } EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); |
d9a3da069 rcu: Add expedite... |
1031 1032 1033 |
#ifdef CONFIG_HOTPLUG_CPU /* |
6cc68793e rcu: fix spelling |
1034 |
* Because preemptible RCU does not exist, there is never any need to |
d9a3da069 rcu: Add expedite... |
1035 1036 1037 1038 1039 1040 1041 1042 1043 |
* report on tasks preempted in RCU read-side critical sections during * expedited RCU grace periods. */ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp) { return; } #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
019129d59 rcu: Stopgap fix ... |
1044 |
/* |
6cc68793e rcu: fix spelling |
1045 |
* Because preemptible RCU does not exist, it never has any work to do. |
f41d911f8 rcu: Merge preemp... |
1046 1047 1048 1049 1050 1051 1052 |
*/ static int rcu_preempt_pending(int cpu) { return 0; } /* |
6cc68793e rcu: fix spelling |
1053 |
* Because preemptible RCU does not exist, it never needs any CPU. |
f41d911f8 rcu: Merge preemp... |
1054 1055 1056 1057 1058 1059 1060 |
*/ static int rcu_preempt_needs_cpu(int cpu) { return 0; } /* |
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, there is no per-CPU |
f41d911f8 rcu: Merge preemp... |
1072 1073 1074 1075 1076 |
* data to initialize. */ static void __cpuinit rcu_preempt_init_percpu_data(int cpu) { } |
1eba8f843 rcu: Clean up cod... |
1077 |
/* |
6cc68793e rcu: fix spelling |
1078 |
* Because there is no preemptible RCU, there are no callbacks to move. |
e74f4c456 rcu: Make hot-unp... |
1079 |
*/ |
29494be71 rcu,cleanup: simp... |
1080 |
static void rcu_preempt_send_cbs_to_online(void) |
e74f4c456 rcu: Make hot-unp... |
1081 1082 1083 1084 |
{ } /* |
6cc68793e rcu: fix spelling |
1085 |
* Because preemptible RCU does not exist, it need not be initialized. |
1eba8f843 rcu: Clean up cod... |
1086 1087 1088 1089 |
*/ static void __init __rcu_init_preempt(void) { } |
f41d911f8 rcu: Merge preemp... |
1090 |
#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ |
8bd93a2c5 rcu: Accelerate g... |
1091 |
|
27f4d2805 rcu: priority boo... |
1092 1093 1094 |
#ifdef CONFIG_RCU_BOOST #include "rtmutex_common.h" |
0ea1f2ebe rcu: Add boosting... |
1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 |
#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 ... |
1108 |
ULONG_CMP_LT(jiffies, rnp->boost_time)) |
0ea1f2ebe rcu: Add boosting... |
1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 |
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 */ |
5342e269b rcu: Permit rt_mu... |
1121 |
static struct lock_class_key rcu_boost_class; |
27f4d2805 rcu: priority boo... |
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 1151 1152 1153 1154 1155 1156 |
/* * 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... |
1157 |
if (rnp->exp_tasks != NULL) { |
27f4d2805 rcu: priority boo... |
1158 |
tb = rnp->exp_tasks; |
0ea1f2ebe rcu: Add boosting... |
1159 1160 |
rnp->n_exp_boosts++; } else { |
27f4d2805 rcu: priority boo... |
1161 |
tb = rnp->boost_tasks; |
0ea1f2ebe rcu: Add boosting... |
1162 1163 1164 |
rnp->n_normal_boosts++; } rnp->n_tasks_boosted++; |
27f4d2805 rcu: priority boo... |
1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 |
/* * 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); |
5342e269b rcu: Permit rt_mu... |
1184 1185 1186 |
/* Avoid lockdep false positives. This rt_mutex is its own thing. */ lockdep_set_class_and_name(&mtx.wait_lock, &rcu_boost_class, "rcu_boost_mutex"); |
27f4d2805 rcu: priority boo... |
1187 |
t->rcu_boost_mutex = &mtx; |
27f4d2805 rcu: priority boo... |
1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 |
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. */ return rnp->exp_tasks != NULL || rnp->boost_tasks != NULL; } /* * Timer handler to initiate waking up of boost kthreads that * have yielded the CPU due to excessive numbers of tasks to * boost. We wake up the per-rcu_node kthread, which in turn * will wake up the booster kthread. */ static void rcu_boost_kthread_timer(unsigned long arg) { |
1217ed1ba rcu: permit rcu_r... |
1203 |
invoke_rcu_node_kthread((struct rcu_node *)arg); |
27f4d2805 rcu: priority boo... |
1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 |
} /* * 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... |
1215 |
trace_rcu_utilization("Start boost kthread@init"); |
27f4d2805 rcu: priority boo... |
1216 |
for (;;) { |
d71df90ea rcu: add tracing ... |
1217 |
rnp->boost_kthread_status = RCU_KTHREAD_WAITING; |
385680a94 rcu: Add event-tr... |
1218 |
trace_rcu_utilization("End boost kthread@rcu_wait"); |
08bca60a6 rcu: Remove waitq... |
1219 |
rcu_wait(rnp->boost_tasks || rnp->exp_tasks); |
385680a94 rcu: Add event-tr... |
1220 |
trace_rcu_utilization("Start boost kthread@rcu_wait"); |
d71df90ea rcu: add tracing ... |
1221 |
rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; |
27f4d2805 rcu: priority boo... |
1222 1223 1224 1225 1226 1227 |
more2boost = rcu_boost(rnp); if (more2boost) spincnt++; else spincnt = 0; if (spincnt > 10) { |
385680a94 rcu: Add event-tr... |
1228 |
trace_rcu_utilization("End boost kthread@rcu_yield"); |
27f4d2805 rcu: priority boo... |
1229 |
rcu_yield(rcu_boost_kthread_timer, (unsigned long)rnp); |
385680a94 rcu: Add event-tr... |
1230 |
trace_rcu_utilization("Start boost kthread@rcu_yield"); |
27f4d2805 rcu: priority boo... |
1231 1232 1233 |
spincnt = 0; } } |
1217ed1ba rcu: permit rcu_r... |
1234 |
/* NOTREACHED */ |
385680a94 rcu: Add event-tr... |
1235 |
trace_rcu_utilization("End boost kthread@notreached"); |
27f4d2805 rcu: priority boo... |
1236 1237 1238 1239 1240 1241 1242 1243 1244 |
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. * |
1217ed1ba rcu: permit rcu_r... |
1245 1246 1247 |
* The caller must hold rnp->lock, which this function releases, * but irqs remain disabled. The ->boost_kthread_task is immortal, * so we don't need to worry about it going away. |
27f4d2805 rcu: priority boo... |
1248 |
*/ |
1217ed1ba rcu: permit rcu_r... |
1249 |
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
27f4d2805 rcu: priority boo... |
1250 1251 |
{ struct task_struct *t; |
0ea1f2ebe rcu: Add boosting... |
1252 1253 |
if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { rnp->n_balk_exp_gp_tasks++; |
1217ed1ba rcu: permit rcu_r... |
1254 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d2805 rcu: priority boo... |
1255 |
return; |
0ea1f2ebe rcu: Add boosting... |
1256 |
} |
27f4d2805 rcu: priority boo... |
1257 1258 1259 1260 1261 1262 1263 |
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... |
1264 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d2805 rcu: priority boo... |
1265 1266 1267 |
t = rnp->boost_kthread_task; if (t != NULL) wake_up_process(t); |
1217ed1ba rcu: permit rcu_r... |
1268 |
} else { |
0ea1f2ebe rcu: Add boosting... |
1269 |
rcu_initiate_boost_trace(rnp); |
1217ed1ba rcu: permit rcu_r... |
1270 1271 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); } |
27f4d2805 rcu: priority boo... |
1272 |
} |
0f962a5e7 rcu: Force per-rc... |
1273 |
/* |
a46e0899e rcu: use softirq ... |
1274 1275 1276 1277 1278 1279 1280 1281 |
* 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... |
1282 1283 1284 |
if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && current != __this_cpu_read(rcu_cpu_kthread_task)) wake_up_process(__this_cpu_read(rcu_cpu_kthread_task)); |
a46e0899e rcu: use softirq ... |
1285 1286 1287 1288 |
local_irq_restore(flags); } /* |
0f962a5e7 rcu: Force per-rc... |
1289 1290 1291 1292 |
* Set the affinity of the boost kthread. The CPU-hotplug locks are * held, so no one should be messing with the existence of the boost * kthread. */ |
27f4d2805 rcu: priority boo... |
1293 1294 1295 |
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, cpumask_var_t cm) { |
27f4d2805 rcu: priority boo... |
1296 |
struct task_struct *t; |
27f4d2805 rcu: priority boo... |
1297 1298 1299 |
t = rnp->boost_kthread_task; if (t != NULL) set_cpus_allowed_ptr(rnp->boost_kthread_task, cm); |
27f4d2805 rcu: priority boo... |
1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 |
} #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... |
1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 |
* 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, struct rcu_node *rnp, int rnp_index) { unsigned long flags; struct sched_param sp; struct task_struct *t; if (&rcu_preempt_state != rsp) return 0; |
a46e0899e rcu: use softirq ... |
1327 |
rsp->boost = 1; |
27f4d2805 rcu: priority boo... |
1328 1329 1330 |
if (rnp->boost_kthread_task != NULL) return 0; t = kthread_create(rcu_boost_kthread, (void *)rnp, |
5b61b0baa rcu: Wire up RCU_... |
1331 |
"rcub/%d", rnp_index); |
27f4d2805 rcu: priority boo... |
1332 1333 1334 1335 1336 |
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_... |
1337 |
sp.sched_priority = RCU_BOOST_PRIO; |
27f4d2805 rcu: priority boo... |
1338 |
sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
9a4327369 rcu: Simplify cur... |
1339 |
wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ |
27f4d2805 rcu: priority boo... |
1340 1341 |
return 0; } |
f8b7fc6b5 rcu: Move RCU_BOO... |
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#ifdef CONFIG_HOTPLUG_CPU /* * Stop the RCU's per-CPU kthread when its CPU goes offline,. */ static void rcu_stop_cpu_kthread(int cpu) { struct task_struct *t; /* Stop the CPU's kthread. */ t = per_cpu(rcu_cpu_kthread_task, cpu); if (t != NULL) { per_cpu(rcu_cpu_kthread_task, cpu) = NULL; kthread_stop(t); } } #endif /* #ifdef CONFIG_HOTPLUG_CPU */ 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(); } /* * Wake up the specified per-rcu_node-structure kthread. * Because the per-rcu_node kthreads are immortal, we don't need * to do anything to keep them alive. */ static void invoke_rcu_node_kthread(struct rcu_node *rnp) { struct task_struct *t; t = rnp->node_kthread_task; if (t != NULL) wake_up_process(t); } /* * Set the specified CPU's kthread to run RT or not, as specified by * the to_rt argument. The CPU-hotplug locks are held, so the task * is not going away. */ static void rcu_cpu_kthread_setrt(int cpu, int to_rt) { int policy; struct sched_param sp; struct task_struct *t; t = per_cpu(rcu_cpu_kthread_task, cpu); if (t == NULL) return; if (to_rt) { policy = SCHED_FIFO; sp.sched_priority = RCU_KTHREAD_PRIO; } else { policy = SCHED_NORMAL; sp.sched_priority = 0; } sched_setscheduler_nocheck(t, policy, &sp); } /* * Timer handler to initiate the waking up of per-CPU kthreads that * have yielded the CPU due to excess numbers of RCU callbacks. * We wake up the per-rcu_node kthread, which in turn will wake up * the booster kthread. */ static void rcu_cpu_kthread_timer(unsigned long arg) { struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg); struct rcu_node *rnp = rdp->mynode; atomic_or(rdp->grpmask, &rnp->wakemask); invoke_rcu_node_kthread(rnp); } /* * Drop to non-real-time priority and yield, but only after posting a * timer that will cause us to regain our real-time priority if we * remain preempted. Either way, we restore our real-time priority * before returning. */ static void rcu_yield(void (*f)(unsigned long), unsigned long arg) { struct sched_param sp; struct timer_list yield_timer; |
5b61b0baa rcu: Wire up RCU_... |
1431 |
int prio = current->rt_priority; |
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1432 1433 1434 1435 1436 1437 1438 |
setup_timer_on_stack(&yield_timer, f, arg); mod_timer(&yield_timer, jiffies + 2); sp.sched_priority = 0; sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp); set_user_nice(current, 19); schedule(); |
5b61b0baa rcu: Wire up RCU_... |
1439 1440 |
set_user_nice(current, 0); sp.sched_priority = prio; |
f8b7fc6b5 rcu: Move RCU_BOO... |
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sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); del_timer(&yield_timer); } /* * Handle cases where the rcu_cpu_kthread() ends up on the wrong CPU. * This can happen while the corresponding CPU is either coming online * or going offline. We cannot wait until the CPU is fully online * before starting the kthread, because the various notifier functions * can wait for RCU grace periods. So we park rcu_cpu_kthread() until * the corresponding CPU is online. * * Return 1 if the kthread needs to stop, 0 otherwise. * * Caller must disable bh. This function can momentarily enable it. */ static int rcu_cpu_kthread_should_stop(int cpu) { while (cpu_is_offline(cpu) || !cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu)) || smp_processor_id() != cpu) { if (kthread_should_stop()) return 1; per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; per_cpu(rcu_cpu_kthread_cpu, cpu) = raw_smp_processor_id(); local_bh_enable(); schedule_timeout_uninterruptible(1); if (!cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu))) set_cpus_allowed_ptr(current, cpumask_of(cpu)); local_bh_disable(); } per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu; return 0; } /* * Per-CPU kernel thread that invokes RCU callbacks. This replaces the |
e0f23060a rcu: Update comme... |
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* RCU softirq used in flavors and configurations of RCU that do not * support RCU priority boosting. |
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*/ static int rcu_cpu_kthread(void *arg) { int cpu = (int)(long)arg; unsigned long flags; int spincnt = 0; unsigned int *statusp = &per_cpu(rcu_cpu_kthread_status, cpu); char work; char *workp = &per_cpu(rcu_cpu_has_work, cpu); |
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trace_rcu_utilization("Start CPU kthread@init"); |
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for (;;) { *statusp = RCU_KTHREAD_WAITING; |
385680a94 rcu: Add event-tr... |
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trace_rcu_utilization("End CPU kthread@rcu_wait"); |
f8b7fc6b5 rcu: Move RCU_BOO... |
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rcu_wait(*workp != 0 || kthread_should_stop()); |
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trace_rcu_utilization("Start CPU kthread@rcu_wait"); |
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local_bh_disable(); if (rcu_cpu_kthread_should_stop(cpu)) { local_bh_enable(); break; } *statusp = RCU_KTHREAD_RUNNING; per_cpu(rcu_cpu_kthread_loops, cpu)++; local_irq_save(flags); work = *workp; *workp = 0; local_irq_restore(flags); if (work) rcu_kthread_do_work(); local_bh_enable(); if (*workp != 0) spincnt++; else spincnt = 0; if (spincnt > 10) { *statusp = RCU_KTHREAD_YIELDING; |
385680a94 rcu: Add event-tr... |
1515 |
trace_rcu_utilization("End CPU kthread@rcu_yield"); |
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1516 |
rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu); |
385680a94 rcu: Add event-tr... |
1517 |
trace_rcu_utilization("Start CPU kthread@rcu_yield"); |
f8b7fc6b5 rcu: Move RCU_BOO... |
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spincnt = 0; } } *statusp = RCU_KTHREAD_STOPPED; |
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1522 |
trace_rcu_utilization("End CPU kthread@term"); |
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return 0; } /* * Spawn a per-CPU kthread, setting up affinity and priority. * Because the CPU hotplug lock is held, no other CPU will be attempting * to manipulate rcu_cpu_kthread_task. There might be another CPU * attempting to access it during boot, but the locking in kthread_bind() * will enforce sufficient ordering. * * Please note that we cannot simply refuse to wake up the per-CPU * kthread because kthreads are created in TASK_UNINTERRUPTIBLE state, * which can result in softlockup complaints if the task ends up being * idle for more than a couple of minutes. * * However, please note also that we cannot bind the per-CPU kthread to its * CPU until that CPU is fully online. We also cannot wait until the * CPU is fully online before we create its per-CPU kthread, as this would * deadlock the system when CPU notifiers tried waiting for grace * periods. So we bind the per-CPU kthread to its CPU only if the CPU * is online. If its CPU is not yet fully online, then the code in * rcu_cpu_kthread() will wait until it is fully online, and then do * the binding. */ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu) { struct sched_param sp; struct task_struct *t; |
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if (!rcu_scheduler_fully_active || |
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per_cpu(rcu_cpu_kthread_task, cpu) != NULL) return 0; |
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t = kthread_create_on_node(rcu_cpu_kthread, (void *)(long)cpu, cpu_to_node(cpu), |
5b61b0baa rcu: Wire up RCU_... |
1557 |
"rcuc/%d", cpu); |
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if (IS_ERR(t)) return PTR_ERR(t); if (cpu_online(cpu)) kthread_bind(t, cpu); per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu; WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL); sp.sched_priority = RCU_KTHREAD_PRIO; sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); per_cpu(rcu_cpu_kthread_task, cpu) = t; wake_up_process(t); /* Get to TASK_INTERRUPTIBLE quickly. */ return 0; } /* * Per-rcu_node kthread, which is in charge of waking up the per-CPU * kthreads when needed. We ignore requests to wake up kthreads * for offline CPUs, which is OK because force_quiescent_state() * takes care of this case. */ static int rcu_node_kthread(void *arg) { int cpu; unsigned long flags; unsigned long mask; struct rcu_node *rnp = (struct rcu_node *)arg; struct sched_param sp; struct task_struct *t; for (;;) { rnp->node_kthread_status = RCU_KTHREAD_WAITING; rcu_wait(atomic_read(&rnp->wakemask) != 0); rnp->node_kthread_status = RCU_KTHREAD_RUNNING; raw_spin_lock_irqsave(&rnp->lock, flags); mask = atomic_xchg(&rnp->wakemask, 0); rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) { if ((mask & 0x1) == 0) continue; preempt_disable(); t = per_cpu(rcu_cpu_kthread_task, cpu); if (!cpu_online(cpu) || t == NULL) { preempt_enable(); continue; } per_cpu(rcu_cpu_has_work, cpu) = 1; sp.sched_priority = RCU_KTHREAD_PRIO; sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); preempt_enable(); } } /* NOTREACHED */ rnp->node_kthread_status = RCU_KTHREAD_STOPPED; return 0; } /* * 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. */ static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) { cpumask_var_t cm; int cpu; unsigned long mask = rnp->qsmaskinit; if (rnp->node_kthread_task == NULL) return; if (!alloc_cpumask_var(&cm, GFP_KERNEL)) return; cpumask_clear(cm); 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); } set_cpus_allowed_ptr(rnp->node_kthread_task, cm); rcu_boost_kthread_setaffinity(rnp, cm); free_cpumask_var(cm); } /* * Spawn a per-rcu_node kthread, setting priority and affinity. * Called during boot before online/offline can happen, or, if * during runtime, with the main CPU-hotplug locks held. So only * one of these can be executing at a time. */ static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp, struct rcu_node *rnp) { unsigned long flags; int rnp_index = rnp - &rsp->node[0]; struct sched_param sp; struct task_struct *t; |
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1660 |
if (!rcu_scheduler_fully_active || |
f8b7fc6b5 rcu: Move RCU_BOO... |
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rnp->qsmaskinit == 0) return 0; if (rnp->node_kthread_task == NULL) { t = kthread_create(rcu_node_kthread, (void *)rnp, |
5b61b0baa rcu: Wire up RCU_... |
1665 |
"rcun/%d", rnp_index); |
f8b7fc6b5 rcu: Move RCU_BOO... |
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if (IS_ERR(t)) return PTR_ERR(t); raw_spin_lock_irqsave(&rnp->lock, flags); rnp->node_kthread_task = t; raw_spin_unlock_irqrestore(&rnp->lock, flags); sp.sched_priority = 99; sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ } return rcu_spawn_one_boost_kthread(rsp, rnp, rnp_index); } /* * Spawn all kthreads -- called as soon as the scheduler is running. */ static int __init rcu_spawn_kthreads(void) { int cpu; struct rcu_node *rnp; |
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1685 |
rcu_scheduler_fully_active = 1; |
f8b7fc6b5 rcu: Move RCU_BOO... |
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for_each_possible_cpu(cpu) { per_cpu(rcu_cpu_has_work, cpu) = 0; if (cpu_online(cpu)) (void)rcu_spawn_one_cpu_kthread(cpu); } rnp = rcu_get_root(rcu_state); (void)rcu_spawn_one_node_kthread(rcu_state, rnp); if (NUM_RCU_NODES > 1) { rcu_for_each_leaf_node(rcu_state, rnp) (void)rcu_spawn_one_node_kthread(rcu_state, rnp); } 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. */ |
b0d304172 rcu: Prevent RCU ... |
1707 |
if (rcu_scheduler_fully_active) { |
f8b7fc6b5 rcu: Move RCU_BOO... |
1708 1709 1710 1711 1712 |
(void)rcu_spawn_one_cpu_kthread(cpu); if (rnp->node_kthread_task == NULL) (void)rcu_spawn_one_node_kthread(rcu_state, rnp); } } |
27f4d2805 rcu: priority boo... |
1713 |
#else /* #ifdef CONFIG_RCU_BOOST */ |
1217ed1ba rcu: permit rcu_r... |
1714 |
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
27f4d2805 rcu: priority boo... |
1715 |
{ |
1217ed1ba rcu: permit rcu_r... |
1716 |
raw_spin_unlock_irqrestore(&rnp->lock, flags); |
27f4d2805 rcu: priority boo... |
1717 |
} |
a46e0899e rcu: use softirq ... |
1718 |
static void invoke_rcu_callbacks_kthread(void) |
27f4d2805 rcu: priority boo... |
1719 |
{ |
a46e0899e rcu: use softirq ... |
1720 |
WARN_ON_ONCE(1); |
27f4d2805 rcu: priority boo... |
1721 1722 1723 1724 1725 |
} static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) { } |
f8b7fc6b5 rcu: Move RCU_BOO... |
1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 |
#ifdef CONFIG_HOTPLUG_CPU static void rcu_stop_cpu_kthread(int cpu) { } #endif /* #ifdef CONFIG_HOTPLUG_CPU */ static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) { } static void rcu_cpu_kthread_setrt(int cpu, int to_rt) { } |
b0d304172 rcu: Prevent RCU ... |
1741 1742 1743 1744 1745 1746 |
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... |
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static void __cpuinit rcu_prepare_kthreads(int cpu) { } |
27f4d2805 rcu: priority boo... |
1750 |
#endif /* #else #ifdef CONFIG_RCU_BOOST */ |
7b27d5475 rcu,cleanup: move... |
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#ifndef CONFIG_SMP void synchronize_sched_expedited(void) { cond_resched(); } EXPORT_SYMBOL_GPL(synchronize_sched_expedited); #else /* #ifndef CONFIG_SMP */ |
e27fc9641 rcu: increase syn... |
1760 1761 |
static atomic_t sync_sched_expedited_started = ATOMIC_INIT(0); static atomic_t sync_sched_expedited_done = ATOMIC_INIT(0); |
7b27d5475 rcu,cleanup: move... |
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static int synchronize_sched_expedited_cpu_stop(void *data) { /* * There must be a full memory barrier on each affected CPU * between the time that try_stop_cpus() is called and the * time that it returns. * * In the current initial implementation of cpu_stop, the * above condition is already met when the control reaches * this point and the following smp_mb() is not strictly * necessary. Do smp_mb() anyway for documentation and * robustness against future implementation changes. */ smp_mb(); /* See above comment block. */ return 0; } /* * Wait for an rcu-sched grace period to elapse, but use "big hammer" * approach to force grace period to end quickly. This consumes * significant time on all CPUs, and is thus not recommended for * any sort of common-case code. * * Note that it is illegal to call this function while holding any * lock that is acquired by a CPU-hotplug notifier. Failing to * observe this restriction will result in deadlock. |
db3a89209 rcu: fix race con... |
1789 |
* |
e27fc9641 rcu: increase syn... |
1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 |
* This implementation can be thought of as an application of ticket * locking to RCU, with sync_sched_expedited_started and * sync_sched_expedited_done taking on the roles of the halves * of the ticket-lock word. Each task atomically increments * sync_sched_expedited_started upon entry, snapshotting the old value, * then attempts to stop all the CPUs. If this succeeds, then each * CPU will have executed a context switch, resulting in an RCU-sched * grace period. We are then done, so we use atomic_cmpxchg() to * update sync_sched_expedited_done to match our snapshot -- but * only if someone else has not already advanced past our snapshot. * * On the other hand, if try_stop_cpus() fails, we check the value * of sync_sched_expedited_done. If it has advanced past our * initial snapshot, then someone else must have forced a grace period * some time after we took our snapshot. In this case, our work is * done for us, and we can simply return. Otherwise, we try again, * but keep our initial snapshot for purposes of checking for someone * doing our work for us. * * If we fail too many times in a row, we fall back to synchronize_sched(). |
7b27d5475 rcu,cleanup: move... |
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*/ void synchronize_sched_expedited(void) { |
e27fc9641 rcu: increase syn... |
1813 |
int firstsnap, s, snap, trycount = 0; |
7b27d5475 rcu,cleanup: move... |
1814 |
|
e27fc9641 rcu: increase syn... |
1815 1816 |
/* Note that atomic_inc_return() implies full memory barrier. */ firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started); |
7b27d5475 rcu,cleanup: move... |
1817 |
get_online_cpus(); |
e27fc9641 rcu: increase syn... |
1818 1819 1820 1821 1822 |
/* * Each pass through the following loop attempts to force a * context switch on each CPU. */ |
7b27d5475 rcu,cleanup: move... |
1823 1824 1825 1826 |
while (try_stop_cpus(cpu_online_mask, synchronize_sched_expedited_cpu_stop, NULL) == -EAGAIN) { put_online_cpus(); |
e27fc9641 rcu: increase syn... |
1827 1828 |
/* No joy, try again later. Or just synchronize_sched(). */ |
7b27d5475 rcu,cleanup: move... |
1829 1830 1831 1832 1833 1834 |
if (trycount++ < 10) udelay(trycount * num_online_cpus()); else { synchronize_sched(); return; } |
e27fc9641 rcu: increase syn... |
1835 1836 1837 1838 |
/* Check to see if someone else did our work for us. */ s = atomic_read(&sync_sched_expedited_done); if (UINT_CMP_GE((unsigned)s, (unsigned)firstsnap)) { |
7b27d5475 rcu,cleanup: move... |
1839 1840 1841 |
smp_mb(); /* ensure test happens before caller kfree */ return; } |
e27fc9641 rcu: increase syn... |
1842 1843 1844 1845 1846 1847 1848 1849 1850 |
/* * Refetching sync_sched_expedited_started allows later * callers to piggyback on our grace period. We subtract * 1 to get the same token that the last incrementer got. * We retry after they started, so our grace period works * for them, and they started after our first try, so their * grace period works for us. */ |
7b27d5475 rcu,cleanup: move... |
1851 |
get_online_cpus(); |
e27fc9641 rcu: increase syn... |
1852 1853 |
snap = atomic_read(&sync_sched_expedited_started) - 1; smp_mb(); /* ensure read is before try_stop_cpus(). */ |
7b27d5475 rcu,cleanup: move... |
1854 |
} |
e27fc9641 rcu: increase syn... |
1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 |
/* * Everyone up to our most recent fetch is covered by our grace * period. Update the counter, but only if our work is still * relevant -- which it won't be if someone who started later * than we did beat us to the punch. */ do { s = atomic_read(&sync_sched_expedited_done); if (UINT_CMP_GE((unsigned)s, (unsigned)snap)) { smp_mb(); /* ensure test happens before caller kfree */ break; } } while (atomic_cmpxchg(&sync_sched_expedited_done, s, snap) != s); |
7b27d5475 rcu,cleanup: move... |
1869 1870 1871 1872 1873 |
put_online_cpus(); } EXPORT_SYMBOL_GPL(synchronize_sched_expedited); #endif /* #else #ifndef CONFIG_SMP */ |
8bd93a2c5 rcu: Accelerate g... |
1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 |
#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. * * Because we have preemptible RCU, just check whether this CPU needs * any flavor of RCU. Do not chew up lots of CPU cycles with preemption * disabled in a most-likely vain attempt to cause RCU not to need this CPU. */ int rcu_needs_cpu(int cpu) { return rcu_needs_cpu_quick_check(cpu); } #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ #define RCU_NEEDS_CPU_FLUSHES 5 |
a47cd880b rcu: Fix accelera... |
1894 |
static DEFINE_PER_CPU(int, rcu_dyntick_drain); |
71da81324 rcu: Fix accelera... |
1895 |
static DEFINE_PER_CPU(unsigned long, rcu_dyntick_holdoff); |
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1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 |
/* * 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. * * Because we are not supporting preemptible RCU, attempt to accelerate * any current grace periods so that RCU no longer needs this CPU, but * only if all other CPUs are already in dynticks-idle mode. This will * allow the CPU cores to be powered down immediately, as opposed to after * waiting many milliseconds for grace periods to elapse. |
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1908 1909 1910 |
* * Because it is not legal to invoke rcu_process_callbacks() with irqs * disabled, we do one pass of force_quiescent_state(), then do a |
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1911 |
* invoke_rcu_core() to cause rcu_process_callbacks() to be invoked |
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1912 |
* later. The per-cpu rcu_dyntick_drain variable controls the sequencing. |
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1913 1914 1915 |
*/ int rcu_needs_cpu(int cpu) { |
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1916 |
int c = 0; |
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1917 |
int snap; |
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1918 |
int thatcpu; |
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1919 1920 1921 |
/* Check for being in the holdoff period. */ if (per_cpu(rcu_dyntick_holdoff, cpu) == jiffies) return rcu_needs_cpu_quick_check(cpu); |
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1922 |
/* Don't bother unless we are the last non-dyntick-idle CPU. */ |
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1923 1924 1925 |
for_each_online_cpu(thatcpu) { if (thatcpu == cpu) continue; |
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1926 1927 |
snap = atomic_add_return(0, &per_cpu(rcu_dynticks, thatcpu).dynticks); |
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1928 |
smp_mb(); /* Order sampling of snap with end of grace period. */ |
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1929 |
if ((snap & 0x1) != 0) { |
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1930 |
per_cpu(rcu_dyntick_drain, cpu) = 0; |
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1931 |
per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1; |
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1932 |
return rcu_needs_cpu_quick_check(cpu); |
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1933 |
} |
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1934 |
} |
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1935 1936 1937 1938 1939 1940 1941 |
/* Check and update the rcu_dyntick_drain sequencing. */ if (per_cpu(rcu_dyntick_drain, cpu) <= 0) { /* First time through, initialize the counter. */ per_cpu(rcu_dyntick_drain, cpu) = RCU_NEEDS_CPU_FLUSHES; } else if (--per_cpu(rcu_dyntick_drain, cpu) <= 0) { /* We have hit the limit, so time to give up. */ |
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1942 |
per_cpu(rcu_dyntick_holdoff, cpu) = jiffies; |
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1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 |
return rcu_needs_cpu_quick_check(cpu); } /* Do one step pushing remaining RCU callbacks through. */ if (per_cpu(rcu_sched_data, cpu).nxtlist) { rcu_sched_qs(cpu); force_quiescent_state(&rcu_sched_state, 0); c = c || per_cpu(rcu_sched_data, cpu).nxtlist; } if (per_cpu(rcu_bh_data, cpu).nxtlist) { rcu_bh_qs(cpu); force_quiescent_state(&rcu_bh_state, 0); c = c || per_cpu(rcu_bh_data, cpu).nxtlist; |
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1956 1957 1958 |
} /* If RCU callbacks are still pending, RCU still needs this CPU. */ |
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1959 |
if (c) |
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1960 |
invoke_rcu_core(); |
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1961 1962 1963 1964 |
return c; } #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |