diff options
| -rw-r--r-- | kernel/smp.c | 162 |
1 files changed, 86 insertions, 76 deletions
diff --git a/kernel/smp.c b/kernel/smp.c index f5308258891a..7ad2262d2eca 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -2,13 +2,12 @@ * 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/module.h> +#include <linux/percpu.h> +#include <linux/init.h> #include <linux/smp.h> #include <linux/cpu.h> @@ -17,29 +16,30 @@ static DEFINE_PER_CPU(struct call_single_queue, call_single_queue); static struct { struct list_head queue; spinlock_t lock; -} call_function __cacheline_aligned_in_smp = { - .queue = LIST_HEAD_INIT(call_function.queue), - .lock = __SPIN_LOCK_UNLOCKED(call_function.lock), -}; +} call_function __cacheline_aligned_in_smp = + { + .queue = LIST_HEAD_INIT(call_function.queue), + .lock = __SPIN_LOCK_UNLOCKED(call_function.lock), + }; enum { CSD_FLAG_LOCK = 0x01, }; struct call_function_data { - struct call_single_data csd; - spinlock_t lock; - unsigned int refs; - cpumask_var_t cpumask; + struct call_single_data csd; + spinlock_t lock; + unsigned int refs; + cpumask_var_t cpumask; }; struct call_single_queue { - struct list_head list; - spinlock_t lock; + struct list_head list; + spinlock_t lock; }; static DEFINE_PER_CPU(struct call_function_data, cfd_data) = { - .lock = __SPIN_LOCK_UNLOCKED(cfd_data.lock), + .lock = __SPIN_LOCK_UNLOCKED(cfd_data.lock), }; static int @@ -71,7 +71,7 @@ hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) } static struct notifier_block __cpuinitdata hotplug_cfd_notifier = { - .notifier_call = hotplug_cfd, + .notifier_call = hotplug_cfd, }; static int __cpuinit init_call_single_data(void) @@ -96,9 +96,9 @@ early_initcall(init_call_single_data); /* * 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. + * 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 *data) { @@ -112,27 +112,29 @@ static void csd_lock(struct call_single_data *data) data->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. + * 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 *data) { WARN_ON(!(data->flags & CSD_FLAG_LOCK)); + /* - * ensure we're all done before releasing data + * ensure we're all done before releasing data: */ smp_mb(); + data->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. + * 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, int wait) @@ -154,10 +156,9 @@ void generic_exec_single(int cpu, struct call_single_data *data, int wait) * 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... + * locking and barrier primitives. Generic code isn't really + * equipped to do the right thing... */ - if (ipi) arch_send_call_function_single_ipi(cpu); @@ -183,8 +184,8 @@ void generic_smp_call_function_interrupt(void) smp_mb(); /* - * It's ok to use list_for_each_rcu() here even though we may delete - * 'pos', since list_del_rcu() doesn't clear ->next + * It's ok to use list_for_each_rcu() here even though we may + * delete 'pos', since list_del_rcu() doesn't clear ->next */ list_for_each_entry_rcu(data, &call_function.queue, csd.list) { int refs; @@ -219,14 +220,14 @@ void generic_smp_call_function_interrupt(void) } /* - * Invoked by arch to handle an IPI for call function single. Must be called - * from the arch with interrupts disabled. + * 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); unsigned int data_flags; + LIST_HEAD(list); spin_lock(&q->lock); list_replace_init(&q->list, &list); @@ -235,22 +236,20 @@ void generic_smp_call_function_single_interrupt(void) while (!list_empty(&list)) { struct call_single_data *data; - data = list_entry(list.next, struct call_single_data, - list); + 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' 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); /* - * Unlocked CSDs are valid through generic_exec_single() + * Unlocked CSDs are valid through generic_exec_single(): */ if (data_flags & CSD_FLAG_LOCK) csd_unlock(data); @@ -276,34 +275,41 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info, .flags = 0, }; unsigned long flags; - /* prevent preemption and reschedule on another processor, - as well as CPU removal */ - int me = get_cpu(); + 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 */ WARN_ON(irqs_disabled()); - if (cpu == me) { + 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 *data = &d; + } else { + if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { + struct call_single_data *data = &d; - if (!wait) - data = &__get_cpu_var(csd_data); + if (!wait) + data = &__get_cpu_var(csd_data); - csd_lock(data); + csd_lock(data); - data->func = func; - data->info = info; - generic_exec_single(cpu, data, wait); - } else { - err = -ENXIO; /* CPU not online */ + data->func = func; + data->info = info; + generic_exec_single(cpu, data, wait); + } else { + err = -ENXIO; /* CPU not online */ + } } put_cpu(); + return err; } EXPORT_SYMBOL(smp_call_function_single); @@ -313,10 +319,9 @@ EXPORT_SYMBOL(smp_call_function_single); * @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. - * + * 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, int wait) @@ -329,10 +334,11 @@ void __smp_call_function_single(int cpu, struct call_single_data *data, generic_exec_single(cpu, data, wait); } -/* FIXME: Shim for archs using old arch_send_call_function_ipi API. */ +/* Deprecated: 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)) +# define arch_send_call_function_ipi_mask(maskp) \ + arch_send_call_function_ipi(*(maskp)) #endif /** @@ -340,7 +346,8 @@ void __smp_call_function_single(int cpu, struct call_single_data *data, * @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. + * @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 @@ -351,27 +358,27 @@ void __smp_call_function_single(int cpu, struct call_single_data *data, * must be disabled when calling this function. */ void smp_call_function_many(const struct cpumask *mask, - void (*func)(void *), void *info, - bool wait) + void (*func)(void *), void *info, bool wait) { struct call_function_data *data; unsigned long flags; - int cpu, next_cpu, me = smp_processor_id(); + int cpu, next_cpu, this_cpu = smp_processor_id(); /* Can deadlock when called with interrupts disabled */ WARN_ON(irqs_disabled()); - /* So, what's a CPU they want? Ignoring this one. */ + /* So, what's a CPU they want? Ignoring this one. */ cpu = cpumask_first_and(mask, cpu_online_mask); - if (cpu == me) + 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 == me) + if (next_cpu == this_cpu) next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); /* Fastpath: do that cpu by itself. */ @@ -387,30 +394,31 @@ void smp_call_function_many(const struct cpumask *mask, data->csd.func = func; data->csd.info = info; cpumask_and(data->cpumask, mask, cpu_online_mask); - cpumask_clear_cpu(me, data->cpumask); + cpumask_clear_cpu(this_cpu, data->cpumask); data->refs = cpumask_weight(data->cpumask); spin_lock(&call_function.lock); /* * Place entry at the _HEAD_ of the list, so that any cpu still - * observing the entry in generic_smp_call_function_interrupt() will - * not miss any other list entries. + * observing the entry in generic_smp_call_function_interrupt() + * will not miss any other list entries: */ list_add_rcu(&data->csd.list, &call_function.queue); spin_unlock(&call_function.lock); + spin_unlock_irqrestore(&data->lock, flags); /* * Make the list addition visible before sending the ipi. - * (IPIs must obey or appear to obey normal Linux cache coherency - * rules -- see comment in generic_exec_single). + * (IPIs must obey or appear to obey normal Linux cache + * coherency rules -- see comment in generic_exec_single). */ smp_mb(); /* Send a message to all CPUs in the map */ arch_send_call_function_ipi_mask(data->cpumask); - /* optionally wait for the CPUs to complete */ + /* Optionally wait for the CPUs to complete */ if (wait) csd_lock_wait(&data->csd); } @@ -420,7 +428,8 @@ 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. + * @wait: If true, wait (atomically) until function has completed + * on other CPUs. * * Returns 0. * @@ -436,6 +445,7 @@ 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); |