diff --git a/kernel/smp.c b/kernel/smp.c index 6ecf4b9895d4e15e1ccb1a25beab3efdbdaa5195..7a0ce25829dccc226b4ae27178ac025b0b2ea8d2 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -10,23 +10,28 @@ #include #include #include +#include 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); + +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), +}; enum { CSD_FLAG_WAIT = 0x01, - CSD_FLAG_ALLOC = 0x02, - CSD_FLAG_LOCK = 0x04, + CSD_FLAG_LOCK = 0x02, }; struct call_function_data { struct call_single_data csd; spinlock_t lock; unsigned int refs; - struct rcu_head rcu_head; - unsigned long cpumask_bits[]; + cpumask_var_t cpumask; }; struct call_single_queue { @@ -34,8 +39,45 @@ struct call_single_queue { spinlock_t lock; }; +static DEFINE_PER_CPU(struct call_function_data, cfd_data) = { + .lock = __SPIN_LOCK_UNLOCKED(cfd_data.lock), +}; + +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 (!alloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, + cpu_to_node(cpu))) + return NOTIFY_BAD; + break; + +#ifdef CONFIG_CPU_HOTPLUG + 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 = { + .notifier_call = hotplug_cfd, +}; + static int __cpuinit init_call_single_data(void) { + void *cpu = (void *)(long)smp_processor_id(); int i; for_each_possible_cpu(i) { @@ -44,18 +86,69 @@ static int __cpuinit init_call_single_data(void) 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); + return 0; } early_initcall(init_call_single_data); -static void csd_flag_wait(struct call_single_data *data) +/* + * csd_wait/csd_complete are used for synchronous ipi calls + */ +static void csd_wait_prepare(struct call_single_data *data) { - /* Wait for response */ - do { - if (!(data->flags & CSD_FLAG_WAIT)) - break; + data->flags |= CSD_FLAG_WAIT; +} + +static void csd_complete(struct call_single_data *data) +{ + if (data->flags & CSD_FLAG_WAIT) { + /* + * ensure we're all done before saying we are + */ + smp_mb(); + data->flags &= ~CSD_FLAG_WAIT; + } +} + +static void csd_wait(struct call_single_data *data) +{ + while (data->flags & CSD_FLAG_WAIT) cpu_relax(); - } while (1); +} + +/* + * 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(struct call_single_data *data) +{ + while (data->flags & CSD_FLAG_LOCK) + cpu_relax(); + 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. + */ + + 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 + */ + smp_mb(); + data->flags &= ~CSD_FLAG_LOCK; } /* @@ -89,16 +182,7 @@ static void generic_exec_single(int cpu, struct call_single_data *data) 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); + csd_wait(data); } /* @@ -122,41 +206,35 @@ void generic_smp_call_function_interrupt(void) * 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) { + list_for_each_entry_rcu(data, &call_function.queue, csd.list) { int refs; - if (!cpumask_test_cpu(cpu, to_cpumask(data->cpumask_bits))) + spin_lock(&data->lock); + if (!cpumask_test_cpu(cpu, data->cpumask)) { + spin_unlock(&data->lock); continue; + } + cpumask_clear_cpu(cpu, data->cpumask); + spin_unlock(&data->lock); 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; + refs = --data->refs; + if (!refs) { + spin_lock(&call_function.lock); + list_del_rcu(&data->csd.list); + spin_unlock(&call_function.lock); + } 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); + csd_complete(&data->csd); + csd_unlock(&data->csd); } - rcu_read_unlock(); put_cpu(); } @@ -192,14 +270,14 @@ void generic_smp_call_function_single_interrupt(void) 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); + if (data_flags & CSD_FLAG_WAIT) + csd_complete(data); + + /* + * Unlocked CSDs are valid through generic_exec_single() + */ + if (data_flags & CSD_FLAG_LOCK) + csd_unlock(data); } } @@ -218,7 +296,9 @@ static DEFINE_PER_CPU(struct call_single_data, csd_data); int smp_call_function_single(int cpu, void (*func) (void *info), void *info, int wait) { - struct call_single_data d; + struct call_single_data d = { + .flags = 0, + }; unsigned long flags; /* prevent preemption and reschedule on another processor, as well as CPU removal */ @@ -239,13 +319,11 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info, /* * 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. + * We 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. @@ -255,18 +333,11 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info, * 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; - } + data = &__get_cpu_var(csd_data); + csd_lock(data); } else { data = &d; - data->flags = CSD_FLAG_WAIT; + csd_wait_prepare(data); } data->func = func; @@ -326,14 +397,14 @@ void smp_call_function_many(const struct cpumask *mask, { struct call_function_data *data; unsigned long flags; - int cpu, next_cpu; + int cpu, next_cpu, me = smp_processor_id(); /* 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()) + if (cpu == me) cpu = cpumask_next_and(cpu, mask, cpu_online_mask); /* No online cpus? We're done. */ if (cpu >= nr_cpu_ids) @@ -341,7 +412,7 @@ void smp_call_function_many(const struct cpumask *mask, /* 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()) + if (next_cpu == me) next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); /* Fastpath: do that cpu by itself. */ @@ -350,31 +421,28 @@ void smp_call_function_many(const struct cpumask *mask, 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; - } + data = &__get_cpu_var(cfd_data); + csd_lock(&data->csd); - spin_lock_init(&data->lock); - data->csd.flags = CSD_FLAG_ALLOC; + spin_lock_irqsave(&data->lock, flags); if (wait) - data->csd.flags |= CSD_FLAG_WAIT; + csd_wait_prepare(&data->csd); + 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)); + cpumask_and(data->cpumask, mask, cpu_online_mask); + cpumask_clear_cpu(me, data->cpumask); + data->refs = cpumask_weight(data->cpumask); - spin_lock_irqsave(&call_function_lock, flags); - list_add_tail_rcu(&data->csd.list, &call_function_queue); - spin_unlock_irqrestore(&call_function_lock, flags); + 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. + */ + 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. @@ -384,11 +452,11 @@ void smp_call_function_many(const struct cpumask *mask, smp_mb(); /* Send a message to all CPUs in the map */ - arch_send_call_function_ipi_mask(to_cpumask(data->cpumask_bits)); + arch_send_call_function_ipi_mask(data->cpumask); /* optionally wait for the CPUs to complete */ if (wait) - csd_flag_wait(&data->csd); + csd_wait(&data->csd); } EXPORT_SYMBOL(smp_call_function_many); @@ -418,20 +486,20 @@ EXPORT_SYMBOL(smp_call_function); void ipi_call_lock(void) { - spin_lock(&call_function_lock); + spin_lock(&call_function.lock); } void ipi_call_unlock(void) { - spin_unlock(&call_function_lock); + spin_unlock(&call_function.lock); } void ipi_call_lock_irq(void) { - spin_lock_irq(&call_function_lock); + spin_lock_irq(&call_function.lock); } void ipi_call_unlock_irq(void) { - spin_unlock_irq(&call_function_lock); + spin_unlock_irq(&call_function.lock); }