/* * Generic helpers for smp ipi calls * * (C) Jens Axboe 2008 */ #include #include #include #include #include #include #include #include #include #include #include "smpboot.h" enum { CSD_FLAG_LOCK = 0x01, }; struct call_function_data { struct call_single_data __percpu *csd; cpumask_var_t cpumask; cpumask_var_t cpumask_ipi; }; static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data); struct call_single_queue { struct list_head list; raw_spinlock_t lock; }; /* CPU mask indicating which CPUs to bring online during smp_init() */ static bool have_boot_cpu_mask; static cpumask_var_t boot_cpu_mask; static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue); static void flush_smp_call_function_queue(bool warn_cpu_offline); 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: if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, cpu_to_node(cpu))) return notifier_from_errno(-ENOMEM); if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL, cpu_to_node(cpu))) return notifier_from_errno(-ENOMEM); cfd->csd = alloc_percpu(struct call_single_data); if (!cfd->csd) { free_cpumask_var(cfd->cpumask); return notifier_from_errno(-ENOMEM); } break; #ifdef CONFIG_HOTPLUG_CPU case CPU_UP_CANCELED: case CPU_UP_CANCELED_FROZEN: /* Fall-through to the CPU_DEAD[_FROZEN] case. */ case CPU_DEAD: case CPU_DEAD_FROZEN: free_cpumask_var(cfd->cpumask); free_cpumask_var(cfd->cpumask_ipi); free_percpu(cfd->csd); break; case CPU_DYING: case CPU_DYING_FROZEN: /* * The IPIs for the smp-call-function callbacks queued by other * CPUs might arrive late, either due to hardware latencies or * because this CPU disabled interrupts (inside stop-machine) * before the IPIs were sent. So flush out any pending callbacks * explicitly (without waiting for the IPIs to arrive), to * ensure that the outgoing CPU doesn't go offline with work * still pending. */ flush_smp_call_function_queue(false); break; #endif }; return NOTIFY_OK; } static struct notifier_block __cpuinitdata hotplug_cfd_notifier = { .notifier_call = hotplug_cfd, }; void __init call_function_init(void) { void *cpu = (void *)(long)smp_processor_id(); int i; for_each_possible_cpu(i) { struct call_single_queue *q = &per_cpu(call_single_queue, i); raw_spin_lock_init(&q->lock); INIT_LIST_HEAD(&q->list); } hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu); register_cpu_notifier(&hotplug_cfd_notifier); } /* * csd_lock/csd_unlock used to serialize access to per-cpu csd resources * * 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. */ static void csd_lock_wait(struct call_single_data *csd) { while (csd->flags & CSD_FLAG_LOCK) cpu_relax(); } static void csd_lock(struct call_single_data *csd) { csd_lock_wait(csd); csd->flags |= CSD_FLAG_LOCK; /* * prevent CPU from reordering the above assignment * to ->flags with any subsequent assignments to other * fields of the specified call_single_data structure: */ smp_mb(); } static void csd_unlock(struct call_single_data *csd) { WARN_ON(!(csd->flags & CSD_FLAG_LOCK)); /* * ensure we're all done before releasing data: */ smp_mb(); csd->flags &= ~CSD_FLAG_LOCK; } /* * Insert a previously allocated call_single_data element * for execution on the given CPU. data must already have * ->func, ->info, and ->flags set. */ static void generic_exec_single(int cpu, struct call_single_data *csd, int wait) { struct call_single_queue *dst = &per_cpu(call_single_queue, cpu); unsigned long flags; int ipi; raw_spin_lock_irqsave(&dst->lock, flags); ipi = list_empty(&dst->list); list_add_tail(&csd->list, &dst->list); raw_spin_unlock_irqrestore(&dst->lock, flags); /* * 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 * locking and barrier primitives. Generic code isn't really * equipped to do the right thing... */ if (ipi) arch_send_call_function_single_ipi(cpu); if (wait) csd_lock_wait(csd); } /** * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks * * Invoked by arch to handle an IPI for call function single. * Must be called with interrupts disabled. */ void generic_smp_call_function_single_interrupt(void) { flush_smp_call_function_queue(true); } /** * flush_smp_call_function_queue - Flush pending smp-call-function callbacks * * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an * offline CPU. Skip this check if set to 'false'. * * Flush any pending smp-call-function callbacks queued on this CPU. This is * invoked by the generic IPI handler, as well as by a CPU about to go offline, * to ensure that all pending IPI callbacks are run before it goes completely * offline. * * Loop through the call_single_queue and run all the queued callbacks. * Must be called with interrupts disabled. */ static void flush_smp_call_function_queue(bool warn_cpu_offline) { struct call_single_queue *q = &__get_cpu_var(call_single_queue); LIST_HEAD(list); static bool warned; WARN_ON(!irqs_disabled()); raw_spin_lock(&q->lock); list_replace_init(&q->list, &list); raw_spin_unlock(&q->lock); /* There shouldn't be any pending callbacks on an offline CPU. */ if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) && !warned && !list_empty(&q->list))) { warned = true; WARN(1, "IPI on offline CPU %d\n", smp_processor_id()); } while (!list_empty(&list)) { struct call_single_data *csd; unsigned int csd_flags; csd = list_entry(list.next, struct call_single_data, list); list_del(&csd->list); /* * 'csd' can be invalid after this call if flags == 0 * (when called through generic_exec_single()), * so save them away before making the call: */ csd_flags = csd->flags; csd->func(csd->info); /* * Unlocked CSDs are valid through generic_exec_single(): */ if (csd_flags & CSD_FLAG_LOCK) csd_unlock(csd); } /* * Handle irq works queued remotely by irq_work_queue_on(). * Smp functions above are typically synchronous so they * better run first since some other CPUs may be busy waiting * for them. */ irq_work_run(); } static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data); /* * 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. * @wait: If true, wait until function has completed on other CPUs. * * Returns 0 on success, else a negative status code. */ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, int wait) { struct call_single_data d = { .flags = 0, }; unsigned long flags; int this_cpu; int err = 0; /* * prevent preemption and reschedule on another processor, * as well as CPU removal */ this_cpu = get_cpu(); /* * 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); if (cpu == this_cpu) { local_irq_save(flags); func(info); local_irq_restore(flags); } else { if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { struct call_single_data *csd = &d; if (!wait) csd = &__get_cpu_var(csd_data); csd_lock(csd); csd->func = func; csd->info = info; generic_exec_single(cpu, csd, wait); } else { err = -ENXIO; /* CPU not online */ } } put_cpu(); return err; } EXPORT_SYMBOL(smp_call_function_single); /* * 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, smp_call_func_t func, void *info, int wait) { 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. */ nodemask = cpumask_of_node(cpu_to_node(cpu)); 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); /** * __smp_call_function_single(): Run a function on a specific CPU * @cpu: The CPU to run on. * @data: Pre-allocated and setup data structure * @wait: If true, wait until function has completed on specified CPU. * * 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. */ void __smp_call_function_single(int cpu, struct call_single_data *csd, int wait) { unsigned int this_cpu; unsigned long flags; this_cpu = get_cpu(); /* * 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); if (cpu == this_cpu) { local_irq_save(flags); csd->func(csd->info); local_irq_restore(flags); } else { csd_lock(csd); generic_exec_single(cpu, csd, wait); } put_cpu(); } /** * 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). * @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 (atomically) until function has completed * on other CPUs. * * If @wait is true, then returns once @func has returned. * * 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. */ void smp_call_function_many(const struct cpumask *mask, smp_call_func_t func, void *info, bool wait) { struct call_function_data *cfd; int cpu, next_cpu, this_cpu = smp_processor_id(); /* * 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 && !early_boot_irqs_disabled); /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */ cpu = cpumask_first_and(mask, cpu_online_mask); if (cpu == this_cpu) cpu = cpumask_next_and(cpu, mask, cpu_online_mask); /* 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); if (next_cpu == this_cpu) 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; } cfd = &__get_cpu_var(cfd_data); cpumask_and(cfd->cpumask, mask, cpu_online_mask); cpumask_clear_cpu(this_cpu, cfd->cpumask); /* Some callers race with other cpus changing the passed mask */ if (unlikely(!cpumask_weight(cfd->cpumask))) return; /* * After we put an entry into the list, cfd->cpumask may be cleared * again when another CPU sends another IPI for a SMP function call, so * cfd->cpumask will be zero. */ cpumask_copy(cfd->cpumask_ipi, cfd->cpumask); for_each_cpu(cpu, cfd->cpumask) { struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu); struct call_single_queue *dst = &per_cpu(call_single_queue, cpu); unsigned long flags; csd_lock(csd); csd->func = func; csd->info = info; raw_spin_lock_irqsave(&dst->lock, flags); list_add_tail(&csd->list, &dst->list); raw_spin_unlock_irqrestore(&dst->lock, flags); } /* Send a message to all CPUs in the map */ arch_send_call_function_ipi_mask(cfd->cpumask_ipi); if (wait) { for_each_cpu(cpu, cfd->cpumask) { struct call_single_data *csd; csd = per_cpu_ptr(cfd->csd, cpu); csd_lock_wait(csd); } } } EXPORT_SYMBOL(smp_call_function_many); /** * 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. * @wait: If true, wait (atomically) until function has completed * on other CPUs. * * Returns 0. * * If @wait is true, then returns once @func has returned; otherwise * it returns just before the target cpu calls @func. * * You must not call this function with disabled interrupts or from a * hardware interrupt handler or from a bottom half handler. */ int smp_call_function(smp_call_func_t func, void *info, int wait) { preempt_disable(); smp_call_function_many(cpu_online_mask, func, info, wait); preempt_enable(); return 0; } EXPORT_SYMBOL(smp_call_function); /* 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=", where is an integer * greater than 0, limits the maximum number of CPUs activated in * SMP mode to . */ 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); static int __init boot_cpus(char *str) { alloc_bootmem_cpumask_var(&boot_cpu_mask); if (cpulist_parse(str, boot_cpu_mask) < 0) { pr_warn("SMP: Incorrect boot_cpus cpumask\n"); return -EINVAL; } have_boot_cpu_mask = true; return 0; } early_param("boot_cpus", boot_cpus); /* 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; } /* Should the given CPU be booted during smp_init() ? */ static inline bool boot_cpu(int cpu) { if (!have_boot_cpu_mask) return true; return cpumask_test_cpu(cpu, boot_cpu_mask); } static inline void free_boot_cpu_mask(void) { if (have_boot_cpu_mask) /* Allocated from boot_cpus() */ free_bootmem_cpumask_var(boot_cpu_mask); } /* Called by boot processor to activate the rest. */ void __init smp_init(void) { unsigned int cpu; idle_threads_init(); /* 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) && boot_cpu(cpu)) cpu_up(cpu); } free_boot_cpu_mask(); /* Any cleanup work */ printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus()); smp_cpus_done(setup_max_cpus); } /* * 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(). */ int on_each_cpu(void (*func) (void *info), void *info, int wait) { unsigned long flags; int ret = 0; preempt_disable(); ret = smp_call_function(func, info, wait); local_irq_save(flags); func(info); local_irq_restore(flags); preempt_enable(); return ret; } EXPORT_SYMBOL(on_each_cpu); /** * on_each_cpu_mask(): Run a function on processors specified by * cpumask, which may include the local processor. * @mask: The set of cpus to run on (only runs on online subset). * @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 (atomically) until function has completed * on other CPUs. * * If @wait is true, then returns once @func has returned. * * You must not call this function with disabled interrupts or * from a hardware interrupt handler or from a bottom half handler. */ void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func, void *info, bool wait) { int cpu = get_cpu(); smp_call_function_many(mask, func, info, wait); if (cpumask_test_cpu(cpu, mask)) { local_irq_disable(); func(info); local_irq_enable(); } put_cpu(); } EXPORT_SYMBOL(on_each_cpu_mask); /* * on_each_cpu_cond(): Call a function on each processor for which * the supplied function cond_func returns true, optionally waiting * for all the required CPUs to finish. This may include the local * processor. * @cond_func: A callback function that is passed a cpu id and * the the info parameter. The function is called * with preemption disabled. The function should * return a blooean value indicating whether to IPI * the specified CPU. * @func: The function to run on all applicable CPUs. * This must be fast and non-blocking. * @info: An arbitrary pointer to pass to both functions. * @wait: If true, wait (atomically) until function has * completed on other CPUs. * @gfp_flags: GFP flags to use when allocating the cpumask * used internally by the function. * * The function might sleep if the GFP flags indicates a non * atomic allocation is allowed. * * Preemption is disabled to protect against CPUs going offline but not online. * CPUs going online during the call will not be seen or sent an IPI. * * You must not call this function with disabled interrupts or * from a hardware interrupt handler or from a bottom half handler. */ void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info), smp_call_func_t func, void *info, bool wait, gfp_t gfp_flags) { cpumask_var_t cpus; int cpu, ret; might_sleep_if(gfp_flags & __GFP_WAIT); if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) { preempt_disable(); for_each_online_cpu(cpu) if (cond_func(cpu, info)) cpumask_set_cpu(cpu, cpus); on_each_cpu_mask(cpus, func, info, wait); preempt_enable(); free_cpumask_var(cpus); } else { /* * No free cpumask, bother. No matter, we'll * just have to IPI them one by one. */ preempt_disable(); for_each_online_cpu(cpu) if (cond_func(cpu, info)) { ret = smp_call_function_single(cpu, func, info, wait); WARN_ON_ONCE(ret); } preempt_enable(); } } EXPORT_SYMBOL(on_each_cpu_cond); static void do_nothing(void *unused) { } /** * kick_all_cpus_sync - Force all cpus out of idle * * Used to synchronize the update of pm_idle function pointer. It's * called after the pointer is updated and returns after the dummy * callback function has been executed on all cpus. The execution of * the function can only happen on the remote cpus after they have * left the idle function which had been called via pm_idle function * pointer. So it's guaranteed that nothing uses the previous pointer * anymore. */ void kick_all_cpus_sync(void) { /* Make sure the change is visible before we kick the cpus */ smp_mb(); smp_call_function(do_nothing, NULL, 1); } EXPORT_SYMBOL_GPL(kick_all_cpus_sync);