/* * Generic helpers for smp ipi calls * * (C) Jens Axboe <jens.axboe@oracle.com> 2008 * */ #include <linux/init.h> #include <linux/module.h> #include <linux/percpu.h> #include <linux/rcupdate.h> #include <linux/rculist.h> #include <linux/smp.h> static DEFINE_PER_CPU(struct call_single_queue, call_single_queue); static LIST_HEAD(call_function_queue); __cacheline_aligned_in_smp DEFINE_SPINLOCK(call_function_lock); enum { CSD_FLAG_WAIT = 0x01, CSD_FLAG_ALLOC = 0x02, CSD_FLAG_LOCK = 0x04, }; struct call_function_data { struct call_single_data csd; spinlock_t lock; unsigned int refs; struct rcu_head rcu_head; unsigned long cpumask_bits[]; }; struct call_single_queue { struct list_head list; spinlock_t lock; }; static int __cpuinit init_call_single_data(void) { int i; for_each_possible_cpu(i) { struct call_single_queue *q = &per_cpu(call_single_queue, i); spin_lock_init(&q->lock); INIT_LIST_HEAD(&q->list); } return 0; } early_initcall(init_call_single_data); static void csd_flag_wait(struct call_single_data *data) { /* Wait for response */ do { if (!(data->flags & CSD_FLAG_WAIT)) break; cpu_relax(); } while (1); } /* * 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 *data) { struct call_single_queue *dst = &per_cpu(call_single_queue, cpu); int wait = data->flags & CSD_FLAG_WAIT, ipi; unsigned long flags; spin_lock_irqsave(&dst->lock, flags); ipi = list_empty(&dst->list); list_add_tail(&data->list, &dst->list); spin_unlock_irqrestore(&dst->lock, flags); /* * Make the list addition visible before sending the ipi. */ smp_mb(); if (ipi) arch_send_call_function_single_ipi(cpu); if (wait) csd_flag_wait(data); } static void rcu_free_call_data(struct rcu_head *head) { struct call_function_data *data; data = container_of(head, struct call_function_data, rcu_head); kfree(data); } /* * 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; int cpu = get_cpu(); /* * It's ok to use list_for_each_rcu() here even though we may delete * 'pos', since list_del_rcu() doesn't clear ->next */ rcu_read_lock(); list_for_each_entry_rcu(data, &call_function_queue, csd.list) { int refs; if (!cpumask_test_cpu(cpu, to_cpumask(data->cpumask_bits))) continue; data->csd.func(data->csd.info); spin_lock(&data->lock); cpumask_clear_cpu(cpu, to_cpumask(data->cpumask_bits)); WARN_ON(data->refs == 0); data->refs--; refs = data->refs; spin_unlock(&data->lock); if (refs) continue; spin_lock(&call_function_lock); list_del_rcu(&data->csd.list); spin_unlock(&call_function_lock); if (data->csd.flags & CSD_FLAG_WAIT) { /* * serialize stores to data with the flag clear * and wakeup */ smp_wmb(); data->csd.flags &= ~CSD_FLAG_WAIT; } if (data->csd.flags & CSD_FLAG_ALLOC) call_rcu(&data->rcu_head, rcu_free_call_data); } rcu_read_unlock(); put_cpu(); } /* * Invoked by arch to handle an IPI for call function single. Must be called * from the arch with interrupts disabled. */ void generic_smp_call_function_single_interrupt(void) { struct call_single_queue *q = &__get_cpu_var(call_single_queue); LIST_HEAD(list); /* * Need to see other stores to list head for checking whether * list is empty without holding q->lock */ smp_read_barrier_depends(); while (!list_empty(&q->list)) { unsigned int data_flags; spin_lock(&q->lock); list_replace_init(&q->list, &list); spin_unlock(&q->lock); while (!list_empty(&list)) { struct call_single_data *data; data = list_entry(list.next, struct call_single_data, list); list_del(&data->list); /* * 'data' can be invalid after this call if * flags == 0 (when called through * generic_exec_single(), so save them away before * making the call. */ data_flags = data->flags; data->func(data->info); if (data_flags & CSD_FLAG_WAIT) { smp_wmb(); data->flags &= ~CSD_FLAG_WAIT; } else if (data_flags & CSD_FLAG_LOCK) { smp_wmb(); data->flags &= ~CSD_FLAG_LOCK; } else if (data_flags & CSD_FLAG_ALLOC) kfree(data); } /* * See comment on outer loop */ smp_read_barrier_depends(); } } static DEFINE_PER_CPU(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. Note that @wait * will be implicitly turned on in case of allocation failures, since * we fall back to on-stack allocation. */ int smp_call_function_single(int cpu, void (*func) (void *info), void *info, int wait) { struct call_single_data d; unsigned long flags; /* prevent preemption and reschedule on another processor, as well as CPU removal */ int me = get_cpu(); int err = 0; /* Can deadlock when called with interrupts disabled */ WARN_ON(irqs_disabled()); if (cpu == me) { local_irq_save(flags); func(info); local_irq_restore(flags); } else if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { struct call_single_data *data; if (!wait) { /* * We are calling a function on a single CPU * and we are not going to wait for it to finish. * We first try to allocate the data, but if we * fail, we fall back to use a per cpu data to pass * the information to that CPU. Since all callers * of this code will use the same data, we must * synchronize the callers to prevent a new caller * from corrupting the data before the callee * can access it. * * The CSD_FLAG_LOCK is used to let us know when * the IPI handler is done with the data. * The first caller will set it, and the callee * will clear it. The next caller must wait for * it to clear before we set it again. This * will make sure the callee is done with the * data before a new caller will use it. */ data = kmalloc(sizeof(*data), GFP_ATOMIC); if (data) data->flags = CSD_FLAG_ALLOC; else { data = &per_cpu(csd_data, me); while (data->flags & CSD_FLAG_LOCK) cpu_relax(); data->flags = CSD_FLAG_LOCK; } } else { data = &d; data->flags = CSD_FLAG_WAIT; } data->func = func; data->info = info; generic_exec_single(cpu, data); } else { err = -ENXIO; /* CPU not online */ } put_cpu(); return err; } EXPORT_SYMBOL(smp_call_function_single); /** * __smp_call_function_single(): Run a function on another CPU * @cpu: The CPU to run on. * @data: Pre-allocated and setup data structure * * 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 *data) { /* Can deadlock when called with interrupts disabled */ WARN_ON((data->flags & CSD_FLAG_WAIT) && irqs_disabled()); generic_exec_single(cpu, data); } /* FIXME: Shim for archs using old arch_send_call_function_ipi API. */ #ifndef arch_send_call_function_ipi_mask #define arch_send_call_function_ipi_mask(maskp) \ arch_send_call_function_ipi(*(maskp)) #endif /** * 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. Note that @wait * will be implicitly turned on in case of allocation failures, since * we fall back to on-stack allocation. * * 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, void (*func)(void *), void *info, bool wait) { struct call_function_data *data; unsigned long flags; int cpu, next_cpu; /* Can deadlock when called with interrupts disabled */ WARN_ON(irqs_disabled()); /* So, what's a CPU they want? Ignoring this one. */ cpu = cpumask_first_and(mask, cpu_online_mask); if (cpu == smp_processor_id()) 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 == smp_processor_id()) 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; } data = kmalloc(sizeof(*data) + cpumask_size(), GFP_ATOMIC); if (unlikely(!data)) { /* Slow path. */ for_each_online_cpu(cpu) { if (cpu == smp_processor_id()) continue; if (cpumask_test_cpu(cpu, mask)) smp_call_function_single(cpu, func, info, wait); } return; } spin_lock_init(&data->lock); data->csd.flags = CSD_FLAG_ALLOC; if (wait) data->csd.flags |= CSD_FLAG_WAIT; data->csd.func = func; data->csd.info = info; cpumask_and(to_cpumask(data->cpumask_bits), mask, cpu_online_mask); cpumask_clear_cpu(smp_processor_id(), to_cpumask(data->cpumask_bits)); data->refs = cpumask_weight(to_cpumask(data->cpumask_bits)); spin_lock_irqsave(&call_function_lock, flags); list_add_tail_rcu(&data->csd.list, &call_function_queue); spin_unlock_irqrestore(&call_function_lock, flags); /* * Make the list addition visible before sending the ipi. */ smp_mb(); /* Send a message to all CPUs in the map */ arch_send_call_function_ipi_mask(to_cpumask(data->cpumask_bits)); /* optionally wait for the CPUs to complete */ if (wait) csd_flag_wait(&data->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. In case of allocation * failure, @wait will be implicitly turned on. * * 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(void (*func)(void *), 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); void ipi_call_lock(void) { spin_lock(&call_function_lock); } void ipi_call_unlock(void) { spin_unlock(&call_function_lock); } void ipi_call_lock_irq(void) { spin_lock_irq(&call_function_lock); } void ipi_call_unlock_irq(void) { spin_unlock_irq(&call_function_lock); }