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kernel/smp.c
18.4 KB
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/* * Generic helpers for smp ipi calls * * (C) Jens Axboe <jens.axboe@oracle.com> 2008 |
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*/ |
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#include <linux/rcupdate.h> |
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#include <linux/rculist.h> |
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#include <linux/kernel.h> |
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#include <linux/export.h> |
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#include <linux/percpu.h> #include <linux/init.h> |
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#include <linux/gfp.h> |
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#include <linux/smp.h> |
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#include <linux/cpu.h> |
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#ifdef CONFIG_USE_GENERIC_SMP_HELPERS |
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static struct { struct list_head queue; |
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raw_spinlock_t lock; |
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} call_function __cacheline_aligned_in_smp = { .queue = LIST_HEAD_INIT(call_function.queue), |
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.lock = __RAW_SPIN_LOCK_UNLOCKED(call_function.lock), |
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}; |
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enum { |
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CSD_FLAG_LOCK = 0x01, |
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}; struct call_function_data { |
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struct call_single_data csd; |
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atomic_t refs; |
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cpumask_var_t cpumask; |
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}; |
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static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data); |
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struct call_single_queue { |
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struct list_head list; |
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raw_spinlock_t lock; |
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}; |
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static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue); |
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static int hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) { long cpu = (long)hcpu; struct call_function_data *cfd = &per_cpu(cfd_data, cpu); switch (action) { case CPU_UP_PREPARE: case CPU_UP_PREPARE_FROZEN: |
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if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, |
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cpu_to_node(cpu))) |
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return notifier_from_errno(-ENOMEM); |
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break; |
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#ifdef CONFIG_HOTPLUG_CPU |
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case CPU_UP_CANCELED: case CPU_UP_CANCELED_FROZEN: case CPU_DEAD: case CPU_DEAD_FROZEN: free_cpumask_var(cfd->cpumask); break; #endif }; return NOTIFY_OK; } static struct notifier_block __cpuinitdata hotplug_cfd_notifier = { |
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.notifier_call = hotplug_cfd, |
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}; |
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void __init call_function_init(void) |
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{ |
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void *cpu = (void *)(long)smp_processor_id(); |
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int i; for_each_possible_cpu(i) { struct call_single_queue *q = &per_cpu(call_single_queue, i); |
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raw_spin_lock_init(&q->lock); |
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INIT_LIST_HEAD(&q->list); } |
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hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu); register_cpu_notifier(&hotplug_cfd_notifier); |
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} |
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/* |
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* csd_lock/csd_unlock used to serialize access to per-cpu csd resources * |
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* For non-synchronous ipi calls the csd can still be in use by the * previous function call. For multi-cpu calls its even more interesting * as we'll have to ensure no other cpu is observing our csd. |
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*/ |
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static void csd_lock_wait(struct call_single_data *data) |
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{ while (data->flags & CSD_FLAG_LOCK) cpu_relax(); |
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} static void csd_lock(struct call_single_data *data) { csd_lock_wait(data); |
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data->flags = CSD_FLAG_LOCK; /* |
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* prevent CPU from reordering the above assignment * to ->flags with any subsequent assignments to other * fields of the specified call_single_data structure: |
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*/ |
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smp_mb(); } static void csd_unlock(struct call_single_data *data) { WARN_ON(!(data->flags & CSD_FLAG_LOCK)); |
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/* |
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* ensure we're all done before releasing data: |
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*/ smp_mb(); |
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data->flags &= ~CSD_FLAG_LOCK; |
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} /* |
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* Insert a previously allocated call_single_data element * for execution on the given CPU. data must already have * ->func, ->info, and ->flags set. |
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*/ |
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static void generic_exec_single(int cpu, struct call_single_data *data, int wait) |
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{ struct call_single_queue *dst = &per_cpu(call_single_queue, cpu); |
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unsigned long flags; |
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int ipi; |
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raw_spin_lock_irqsave(&dst->lock, flags); |
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ipi = list_empty(&dst->list); list_add_tail(&data->list, &dst->list); |
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raw_spin_unlock_irqrestore(&dst->lock, flags); |
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/* |
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* The list addition should be visible before sending the IPI * handler locks the list to pull the entry off it because of * normal cache coherency rules implied by spinlocks. * * If IPIs can go out of order to the cache coherency protocol * in an architecture, sufficient synchronisation should be added * to arch code to make it appear to obey cache coherency WRT |
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* locking and barrier primitives. Generic code isn't really * equipped to do the right thing... |
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*/ |
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if (ipi) arch_send_call_function_single_ipi(cpu); if (wait) |
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csd_lock_wait(data); |
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} /* * Invoked by arch to handle an IPI for call function. Must be called with * interrupts disabled. */ void generic_smp_call_function_interrupt(void) { struct call_function_data *data; |
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int cpu = smp_processor_id(); |
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/* |
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* Shouldn't receive this interrupt on a cpu that is not yet online. */ WARN_ON_ONCE(!cpu_online(cpu)); /* |
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* Ensure entry is visible on call_function_queue after we have * entered the IPI. See comment in smp_call_function_many. * If we don't have this, then we may miss an entry on the list * and never get another IPI to process it. */ smp_mb(); /* |
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* It's ok to use list_for_each_rcu() here even though we may * delete 'pos', since list_del_rcu() doesn't clear ->next |
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*/ |
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list_for_each_entry_rcu(data, &call_function.queue, csd.list) { |
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int refs; |
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smp_call_func_t func; |
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/* * Since we walk the list without any locks, we might * see an entry that was completed, removed from the * list and is in the process of being reused. * * We must check that the cpu is in the cpumask before * checking the refs, and both must be set before * executing the callback on this cpu. */ if (!cpumask_test_cpu(cpu, data->cpumask)) continue; smp_rmb(); if (atomic_read(&data->refs) == 0) continue; |
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func = data->csd.func; /* save for later warn */ func(data->csd.info); |
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/* |
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* If the cpu mask is not still set then func enabled * interrupts (BUG), and this cpu took another smp call * function interrupt and executed func(info) twice * on this cpu. That nested execution decremented refs. |
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*/ if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) { |
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WARN(1, "%pf enabled interrupts and double executed ", func); |
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continue; } |
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refs = atomic_dec_return(&data->refs); WARN_ON(refs < 0); |
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if (refs) continue; |
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WARN_ON(!cpumask_empty(data->cpumask)); raw_spin_lock(&call_function.lock); list_del_rcu(&data->csd.list); raw_spin_unlock(&call_function.lock); |
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csd_unlock(&data->csd); |
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} |
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} /* |
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* Invoked by arch to handle an IPI for call function single. Must be * called from the arch with interrupts disabled. |
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*/ void generic_smp_call_function_single_interrupt(void) { struct call_single_queue *q = &__get_cpu_var(call_single_queue); |
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unsigned int data_flags; |
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LIST_HEAD(list); |
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/* * Shouldn't receive this interrupt on a cpu that is not yet online. */ WARN_ON_ONCE(!cpu_online(smp_processor_id())); |
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raw_spin_lock(&q->lock); |
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list_replace_init(&q->list, &list); |
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raw_spin_unlock(&q->lock); |
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while (!list_empty(&list)) { struct call_single_data *data; |
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data = list_entry(list.next, struct call_single_data, list); |
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list_del(&data->list); |
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/* |
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* 'data' can be invalid after this call if flags == 0 * (when called through generic_exec_single()), * so save them away before making the call: |
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*/ |
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data_flags = data->flags; data->func(data->info); |
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/* |
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* Unlocked CSDs are valid through generic_exec_single(): |
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*/ if (data_flags & CSD_FLAG_LOCK) csd_unlock(data); |
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} } |
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static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data); |
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/* * smp_call_function_single - Run a function on a specific CPU * @func: The function to run. This must be fast and non-blocking. * @info: An arbitrary pointer to pass to the function. |
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* @wait: If true, wait until function has completed on other CPUs. * |
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* Returns 0 on success, else a negative status code. |
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*/ |
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int smp_call_function_single(int cpu, smp_call_func_t func, void *info, |
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int wait) |
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{ |
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struct call_single_data d = { .flags = 0, }; |
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unsigned long flags; |
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int this_cpu; |
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int err = 0; |
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/* * prevent preemption and reschedule on another processor, * as well as CPU removal */ this_cpu = get_cpu(); |
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/* * Can deadlock when called with interrupts disabled. * We allow cpu's that are not yet online though, as no one else can * send smp call function interrupt to this cpu and as such deadlocks * can't happen. */ WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() && !oops_in_progress); |
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if (cpu == this_cpu) { |
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local_irq_save(flags); func(info); local_irq_restore(flags); |
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} else { if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { struct call_single_data *data = &d; |
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if (!wait) data = &__get_cpu_var(csd_data); |
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csd_lock(data); |
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data->func = func; data->info = info; generic_exec_single(cpu, data, wait); } else { err = -ENXIO; /* CPU not online */ } |
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} put_cpu(); |
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return err; |
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} EXPORT_SYMBOL(smp_call_function_single); |
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/* * smp_call_function_any - Run a function on any of the given cpus * @mask: The mask of cpus it can run on. * @func: The function to run. This must be fast and non-blocking. * @info: An arbitrary pointer to pass to the function. * @wait: If true, wait until function has completed. * * Returns 0 on success, else a negative status code (if no cpus were online). * Note that @wait will be implicitly turned on in case of allocation failures, * since we fall back to on-stack allocation. * * Selection preference: * 1) current cpu if in @mask * 2) any cpu of current node if in @mask * 3) any other online cpu in @mask */ int smp_call_function_any(const struct cpumask *mask, |
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smp_call_func_t func, void *info, int wait) |
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{ unsigned int cpu; const struct cpumask *nodemask; int ret; /* Try for same CPU (cheapest) */ cpu = get_cpu(); if (cpumask_test_cpu(cpu, mask)) goto call; /* Try for same node. */ |
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nodemask = cpumask_of_node(cpu_to_node(cpu)); |
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for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids; cpu = cpumask_next_and(cpu, nodemask, mask)) { if (cpu_online(cpu)) goto call; } /* Any online will do: smp_call_function_single handles nr_cpu_ids. */ cpu = cpumask_any_and(mask, cpu_online_mask); call: ret = smp_call_function_single(cpu, func, info, wait); put_cpu(); return ret; } EXPORT_SYMBOL_GPL(smp_call_function_any); |
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/** |
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* __smp_call_function_single(): Run a function on a specific CPU |
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* @cpu: The CPU to run on. * @data: Pre-allocated and setup data structure |
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* @wait: If true, wait until function has completed on specified CPU. |
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* |
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* Like smp_call_function_single(), but allow caller to pass in a * pre-allocated data structure. Useful for embedding @data inside * other structures, for instance. |
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*/ |
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void __smp_call_function_single(int cpu, struct call_single_data *data, int wait) |
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{ |
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unsigned int this_cpu; unsigned long flags; |
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this_cpu = get_cpu(); |
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/* * Can deadlock when called with interrupts disabled. * We allow cpu's that are not yet online though, as no one else can * send smp call function interrupt to this cpu and as such deadlocks * can't happen. */ WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled() && !oops_in_progress); |
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if (cpu == this_cpu) { local_irq_save(flags); data->func(data->info); local_irq_restore(flags); } else { csd_lock(data); generic_exec_single(cpu, data, wait); } put_cpu(); |
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} /** |
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* smp_call_function_many(): Run a function on a set of other CPUs. * @mask: The set of cpus to run on (only runs on online subset). |
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* @func: The function to run. This must be fast and non-blocking. * @info: An arbitrary pointer to pass to the function. |
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* @wait: If true, wait (atomically) until function has completed * on other CPUs. |
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* |
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* If @wait is true, then returns once @func has returned. |
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* * You must not call this function with disabled interrupts or from a * hardware interrupt handler or from a bottom half handler. Preemption * must be disabled when calling this function. */ |
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void smp_call_function_many(const struct cpumask *mask, |
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smp_call_func_t func, void *info, bool wait) |
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{ |
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struct call_function_data *data; |
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unsigned long flags; |
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int refs, cpu, next_cpu, this_cpu = smp_processor_id(); |
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/* * Can deadlock when called with interrupts disabled. * We allow cpu's that are not yet online though, as no one else can * send smp call function interrupt to this cpu and as such deadlocks * can't happen. */ WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() |
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&& !oops_in_progress && !early_boot_irqs_disabled); |
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/* Try to fastpath. So, what's a CPU they want? Ignoring this one. */ |
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cpu = cpumask_first_and(mask, cpu_online_mask); |
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if (cpu == this_cpu) |
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cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
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/* No online cpus? We're done. */ if (cpu >= nr_cpu_ids) return; /* Do we have another CPU which isn't us? */ next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
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if (next_cpu == this_cpu) |
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next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); /* Fastpath: do that cpu by itself. */ if (next_cpu >= nr_cpu_ids) { smp_call_function_single(cpu, func, info, wait); return; |
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} |
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data = &__get_cpu_var(cfd_data); csd_lock(&data->csd); |
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/* This BUG_ON verifies our reuse assertions and can be removed */ BUG_ON(atomic_read(&data->refs) || !cpumask_empty(data->cpumask)); |
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/* |
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* The global call function queue list add and delete are protected * by a lock, but the list is traversed without any lock, relying * on the rcu list add and delete to allow safe concurrent traversal. |
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* We reuse the call function data without waiting for any grace * period after some other cpu removes it from the global queue. |
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* This means a cpu might find our data block as it is being * filled out. * * We hold off the interrupt handler on the other cpu by * ordering our writes to the cpu mask vs our setting of the * refs counter. We assert only the cpu owning the data block * will set a bit in cpumask, and each bit will only be cleared * by the subject cpu. Each cpu must first find its bit is * set and then check that refs is set indicating the element is * ready to be processed, otherwise it must skip the entry. * * On the previous iteration refs was set to 0 by another cpu. * To avoid the use of transitivity, set the counter to 0 here * so the wmb will pair with the rmb in the interrupt handler. |
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*/ |
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atomic_set(&data->refs, 0); /* convert 3rd to 1st party write */ data->csd.func = func; data->csd.info = info; /* Ensure 0 refs is visible before mask. Also orders func and info */ smp_wmb(); /* We rely on the "and" being processed before the store */ cpumask_and(data->cpumask, mask, cpu_online_mask); cpumask_clear_cpu(this_cpu, data->cpumask); |
723aae25d
|
502 503 504 505 506 507 508 |
refs = cpumask_weight(data->cpumask); /* Some callers race with other cpus changing the passed mask */ if (unlikely(!refs)) { csd_unlock(&data->csd); return; } |
3d4422332
|
509 |
|
9f5a5621e
|
510 |
raw_spin_lock_irqsave(&call_function.lock, flags); |
8969a5ede
|
511 512 |
/* * Place entry at the _HEAD_ of the list, so that any cpu still |
0b13fda1e
|
513 514 |
* observing the entry in generic_smp_call_function_interrupt() * will not miss any other list entries: |
8969a5ede
|
515 516 |
*/ list_add_rcu(&data->csd.list, &call_function.queue); |
e6cd1e07a
|
517 |
/* |
45a579192
|
518 519 520 |
* We rely on the wmb() in list_add_rcu to complete our writes * to the cpumask before this write to refs, which indicates * data is on the list and is ready to be processed. |
e6cd1e07a
|
521 |
*/ |
723aae25d
|
522 |
atomic_set(&data->refs, refs); |
9f5a5621e
|
523 |
raw_spin_unlock_irqrestore(&call_function.lock, flags); |
3d4422332
|
524 |
|
561920a0d
|
525 526 |
/* * Make the list addition visible before sending the ipi. |
0b13fda1e
|
527 528 |
* (IPIs must obey or appear to obey normal Linux cache * coherency rules -- see comment in generic_exec_single). |
561920a0d
|
529 530 |
*/ smp_mb(); |
3d4422332
|
531 |
/* Send a message to all CPUs in the map */ |
8969a5ede
|
532 |
arch_send_call_function_ipi_mask(data->cpumask); |
3d4422332
|
533 |
|
0b13fda1e
|
534 |
/* Optionally wait for the CPUs to complete */ |
54b11e6d5
|
535 |
if (wait) |
6e2756376
|
536 |
csd_lock_wait(&data->csd); |
3d4422332
|
537 |
} |
54b11e6d5
|
538 |
EXPORT_SYMBOL(smp_call_function_many); |
3d4422332
|
539 540 541 542 543 |
/** * smp_call_function(): Run a function on all other CPUs. * @func: The function to run. This must be fast and non-blocking. * @info: An arbitrary pointer to pass to the function. |
0b13fda1e
|
544 545 |
* @wait: If true, wait (atomically) until function has completed * on other CPUs. |
3d4422332
|
546 |
* |
54b11e6d5
|
547 |
* Returns 0. |
3d4422332
|
548 549 |
* * If @wait is true, then returns once @func has returned; otherwise |
72f279b25
|
550 |
* it returns just before the target cpu calls @func. |
3d4422332
|
551 552 553 554 |
* * You must not call this function with disabled interrupts or from a * hardware interrupt handler or from a bottom half handler. */ |
3a5f65df5
|
555 |
int smp_call_function(smp_call_func_t func, void *info, int wait) |
3d4422332
|
556 |
{ |
3d4422332
|
557 |
preempt_disable(); |
54b11e6d5
|
558 |
smp_call_function_many(cpu_online_mask, func, info, wait); |
3d4422332
|
559 |
preempt_enable(); |
0b13fda1e
|
560 |
|
54b11e6d5
|
561 |
return 0; |
3d4422332
|
562 563 564 565 566 |
} EXPORT_SYMBOL(smp_call_function); void ipi_call_lock(void) { |
9f5a5621e
|
567 |
raw_spin_lock(&call_function.lock); |
3d4422332
|
568 569 570 571 |
} void ipi_call_unlock(void) { |
9f5a5621e
|
572 |
raw_spin_unlock(&call_function.lock); |
3d4422332
|
573 574 575 576 |
} void ipi_call_lock_irq(void) { |
9f5a5621e
|
577 |
raw_spin_lock_irq(&call_function.lock); |
3d4422332
|
578 579 580 581 |
} void ipi_call_unlock_irq(void) { |
9f5a5621e
|
582 |
raw_spin_unlock_irq(&call_function.lock); |
3d4422332
|
583 |
} |
351f8f8e6
|
584 |
#endif /* USE_GENERIC_SMP_HELPERS */ |
34db18a05
|
585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 |
/* Setup configured maximum number of CPUs to activate */ unsigned int setup_max_cpus = NR_CPUS; EXPORT_SYMBOL(setup_max_cpus); /* * Setup routine for controlling SMP activation * * Command-line option of "nosmp" or "maxcpus=0" will disable SMP * activation entirely (the MPS table probe still happens, though). * * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer * greater than 0, limits the maximum number of CPUs activated in * SMP mode to <NUM>. */ void __weak arch_disable_smp_support(void) { } static int __init nosmp(char *str) { setup_max_cpus = 0; arch_disable_smp_support(); return 0; } early_param("nosmp", nosmp); /* this is hard limit */ static int __init nrcpus(char *str) { int nr_cpus; get_option(&str, &nr_cpus); if (nr_cpus > 0 && nr_cpus < nr_cpu_ids) nr_cpu_ids = nr_cpus; return 0; } early_param("nr_cpus", nrcpus); static int __init maxcpus(char *str) { get_option(&str, &setup_max_cpus); if (setup_max_cpus == 0) arch_disable_smp_support(); return 0; } early_param("maxcpus", maxcpus); /* Setup number of possible processor ids */ int nr_cpu_ids __read_mostly = NR_CPUS; EXPORT_SYMBOL(nr_cpu_ids); /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */ void __init setup_nr_cpu_ids(void) { nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1; } /* Called by boot processor to activate the rest. */ void __init smp_init(void) { unsigned int cpu; /* FIXME: This should be done in userspace --RR */ for_each_present_cpu(cpu) { if (num_online_cpus() >= setup_max_cpus) break; if (!cpu_online(cpu)) cpu_up(cpu); } /* Any cleanup work */ printk(KERN_INFO "Brought up %ld CPUs ", (long)num_online_cpus()); smp_cpus_done(setup_max_cpus); } |
351f8f8e6
|
666 |
/* |
bd924e8cb
|
667 668 669 |
* Call a function on all processors. May be used during early boot while * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead * of local_irq_disable/enable(). |
351f8f8e6
|
670 671 672 |
*/ int on_each_cpu(void (*func) (void *info), void *info, int wait) { |
bd924e8cb
|
673 |
unsigned long flags; |
351f8f8e6
|
674 675 676 677 |
int ret = 0; preempt_disable(); ret = smp_call_function(func, info, wait); |
bd924e8cb
|
678 |
local_irq_save(flags); |
351f8f8e6
|
679 |
func(info); |
bd924e8cb
|
680 |
local_irq_restore(flags); |
351f8f8e6
|
681 682 683 684 |
preempt_enable(); return ret; } EXPORT_SYMBOL(on_each_cpu); |