From 3d4422332711ef48ef0f132f1fcbfcbd56c7f3d1 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 26 Jun 2008 11:21:34 +0200 Subject: Add generic helpers for arch IPI function calls This adds kernel/smp.c which contains helpers for IPI function calls. In addition to supporting the existing smp_call_function() in a more efficient manner, it also adds a more scalable variant called smp_call_function_single() for calling a given function on a single CPU only. The core of this is based on the x86-64 patch from Nick Piggin, lots of changes since then. "Alan D. Brunelle" has contributed lots of fixes and suggestions as well. Also thanks to Paul E. McKenney for reviewing RCU usage and getting rid of the data allocation fallback deadlock. Acked-by: Ingo Molnar Reviewed-by: Paul E. McKenney Signed-off-by: Jens Axboe --- kernel/Makefile | 1 + kernel/smp.c | 383 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 384 insertions(+) create mode 100644 kernel/smp.c (limited to 'kernel') diff --git a/kernel/Makefile b/kernel/Makefile index 1c9938addb9..9fa57976f25 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -28,6 +28,7 @@ obj-$(CONFIG_DEBUG_RT_MUTEXES) += rtmutex-debug.o obj-$(CONFIG_RT_MUTEX_TESTER) += rtmutex-tester.o obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o obj-$(CONFIG_SMP) += cpu.o spinlock.o +obj-$(CONFIG_USE_GENERIC_SMP_HELPERS) += smp.o obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o obj-$(CONFIG_PROVE_LOCKING) += spinlock.o obj-$(CONFIG_UID16) += uid16.o diff --git a/kernel/smp.c b/kernel/smp.c new file mode 100644 index 00000000000..f77b75c027a --- /dev/null +++ b/kernel/smp.c @@ -0,0 +1,383 @@ +/* + * Generic helpers for smp ipi calls + * + * (C) Jens Axboe 2008 + * + */ +#include +#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); + +enum { + CSD_FLAG_WAIT = 0x01, + CSD_FLAG_ALLOC = 0x02, +}; + +struct call_function_data { + struct call_single_data csd; + spinlock_t lock; + unsigned int refs; + cpumask_t cpumask; + struct rcu_head rcu_head; +}; + +struct call_single_queue { + struct list_head list; + spinlock_t lock; +}; + +void __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); + } +} + +static void csd_flag_wait(struct call_single_data *data) +{ + /* Wait for response */ + do { + /* + * We need to see the flags store in the IPI handler + */ + smp_mb(); + 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); + + 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 (!cpu_isset(cpu, data->cpumask)) + continue; + + data->csd.func(data->csd.info); + + spin_lock(&data->lock); + cpu_clear(cpu, data->cpumask); + 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; + } else + 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_mb(); + 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_ALLOC) + kfree(data); + } + /* + * See comment on outer loop + */ + smp_mb(); + } +} + +/* + * 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. + * @retry: Unused + * @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 retry, int wait) +{ + struct call_single_data d; + unsigned long flags; + /* prevent preemption and reschedule on another processor */ + int me = get_cpu(); + + /* 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 { + struct call_single_data *data = NULL; + + if (!wait) { + data = kmalloc(sizeof(*data), GFP_ATOMIC); + if (data) + data->flags = CSD_FLAG_ALLOC; + } + if (!data) { + data = &d; + data->flags = CSD_FLAG_WAIT; + } + + data->func = func; + data->info = info; + generic_exec_single(cpu, data); + } + + put_cpu(); + return 0; +} +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); +} + +/** + * smp_call_function_mask(): Run a function on a set of other CPUs. + * @mask: The set of cpus to 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 (atomically) until function has completed on other CPUs. + * + * Returns 0 on success, else a negative status code. + * + * 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. + */ +int smp_call_function_mask(cpumask_t mask, void (*func)(void *), void *info, + int wait) +{ + struct call_function_data d; + struct call_function_data *data = NULL; + cpumask_t allbutself; + unsigned long flags; + int cpu, num_cpus; + + /* Can deadlock when called with interrupts disabled */ + WARN_ON(irqs_disabled()); + + cpu = smp_processor_id(); + allbutself = cpu_online_map; + cpu_clear(cpu, allbutself); + cpus_and(mask, mask, allbutself); + num_cpus = cpus_weight(mask); + + /* + * If zero CPUs, return. If just a single CPU, turn this request + * into a targetted single call instead since it's faster. + */ + if (!num_cpus) + return 0; + else if (num_cpus == 1) { + cpu = first_cpu(mask); + return smp_call_function_single(cpu, func, info, 0, wait); + } + + if (!wait) { + data = kmalloc(sizeof(*data), GFP_ATOMIC); + if (data) + data->csd.flags = CSD_FLAG_ALLOC; + } + if (!data) { + data = &d; + data->csd.flags = CSD_FLAG_WAIT; + } + + spin_lock_init(&data->lock); + data->csd.func = func; + data->csd.info = info; + data->refs = num_cpus; + data->cpumask = mask; + + spin_lock_irqsave(&call_function_lock, flags); + list_add_tail_rcu(&data->csd.list, &call_function_queue); + spin_unlock_irqrestore(&call_function_lock, flags); + + /* Send a message to all CPUs in the map */ + arch_send_call_function_ipi(mask); + + /* optionally wait for the CPUs to complete */ + if (wait) + csd_flag_wait(&data->csd); + + return 0; +} +EXPORT_SYMBOL(smp_call_function_mask); + +/** + * 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. + * @natomic: Unused + * @wait: If true, wait (atomically) until function has completed on other CPUs. + * + * Returns 0 on success, else a negative status code. + * + * 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 natomic, int wait) +{ + int ret; + + preempt_disable(); + ret = smp_call_function_mask(cpu_online_map, func, info, wait); + preempt_enable(); + return ret; +} +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); +} -- cgit v1.2.3 From 8691e5a8f691cc2a4fda0651e8d307aaba0e7d68 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 6 Jun 2008 11:18:06 +0200 Subject: smp_call_function: get rid of the unused nonatomic/retry argument It's never used and the comments refer to nonatomic and retry interchangably. So get rid of it. Acked-by: Jeremy Fitzhardinge Signed-off-by: Jens Axboe --- kernel/smp.c | 6 ++---- kernel/softirq.c | 2 +- kernel/time/tick-broadcast.c | 2 +- 3 files changed, 4 insertions(+), 6 deletions(-) (limited to 'kernel') diff --git a/kernel/smp.c b/kernel/smp.c index f77b75c027a..7e0432a4a0e 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -195,7 +195,6 @@ void generic_smp_call_function_single_interrupt(void) * 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. - * @retry: Unused * @wait: If true, wait until function has completed on other CPUs. * * Returns 0 on success, else a negative status code. Note that @wait @@ -203,7 +202,7 @@ void generic_smp_call_function_single_interrupt(void) * we fall back to on-stack allocation. */ int smp_call_function_single(int cpu, void (*func) (void *info), void *info, - int retry, int wait) + int wait) { struct call_single_data d; unsigned long flags; @@ -339,7 +338,6 @@ EXPORT_SYMBOL(smp_call_function_mask); * 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. - * @natomic: Unused * @wait: If true, wait (atomically) until function has completed on other CPUs. * * Returns 0 on success, else a negative status code. @@ -351,7 +349,7 @@ EXPORT_SYMBOL(smp_call_function_mask); * 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 natomic, int wait) +int smp_call_function(void (*func)(void *), void *info, int wait) { int ret; diff --git a/kernel/softirq.c b/kernel/softirq.c index 36e06174004..d73afb4764e 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -679,7 +679,7 @@ int on_each_cpu(void (*func) (void *info), void *info, int retry, int wait) int ret = 0; preempt_disable(); - ret = smp_call_function(func, info, retry, wait); + ret = smp_call_function(func, info, wait); local_irq_disable(); func(info); local_irq_enable(); diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index 57a1f02e5ec..75e718539dc 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -266,7 +266,7 @@ void tick_broadcast_on_off(unsigned long reason, int *oncpu) "offline CPU #%d\n", *oncpu); else smp_call_function_single(*oncpu, tick_do_broadcast_on_off, - &reason, 1, 1); + &reason, 1); } /* -- cgit v1.2.3 From 15c8b6c1aaaf1c4edd67e2f02e4d8e1bd1a51c0d Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 9 May 2008 09:39:44 +0200 Subject: on_each_cpu(): kill unused 'retry' parameter It's not even passed on to smp_call_function() anymore, since that was removed. So kill it. Acked-by: Jeremy Fitzhardinge Reviewed-by: Paul E. McKenney Signed-off-by: Jens Axboe --- kernel/hrtimer.c | 2 +- kernel/profile.c | 6 +++--- kernel/rcupdate.c | 2 +- kernel/softirq.c | 2 +- 4 files changed, 6 insertions(+), 6 deletions(-) (limited to 'kernel') diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 421be5fe5cc..50e8616d795 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -623,7 +623,7 @@ static void retrigger_next_event(void *arg) void clock_was_set(void) { /* Retrigger the CPU local events everywhere */ - on_each_cpu(retrigger_next_event, NULL, 0, 1); + on_each_cpu(retrigger_next_event, NULL, 1); } /* diff --git a/kernel/profile.c b/kernel/profile.c index ae7ead82cbc..58926411eb2 100644 --- a/kernel/profile.c +++ b/kernel/profile.c @@ -252,7 +252,7 @@ static void profile_flip_buffers(void) mutex_lock(&profile_flip_mutex); j = per_cpu(cpu_profile_flip, get_cpu()); put_cpu(); - on_each_cpu(__profile_flip_buffers, NULL, 0, 1); + on_each_cpu(__profile_flip_buffers, NULL, 1); for_each_online_cpu(cpu) { struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j]; for (i = 0; i < NR_PROFILE_HIT; ++i) { @@ -275,7 +275,7 @@ static void profile_discard_flip_buffers(void) mutex_lock(&profile_flip_mutex); i = per_cpu(cpu_profile_flip, get_cpu()); put_cpu(); - on_each_cpu(__profile_flip_buffers, NULL, 0, 1); + on_each_cpu(__profile_flip_buffers, NULL, 1); for_each_online_cpu(cpu) { struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i]; memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit)); @@ -558,7 +558,7 @@ static int __init create_hash_tables(void) out_cleanup: prof_on = 0; smp_mb(); - on_each_cpu(profile_nop, NULL, 0, 1); + on_each_cpu(profile_nop, NULL, 1); for_each_online_cpu(cpu) { struct page *page; diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index c09605f8d16..6addab5e6d8 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -127,7 +127,7 @@ void rcu_barrier(void) * until all the callbacks are queued. */ rcu_read_lock(); - on_each_cpu(rcu_barrier_func, NULL, 0, 1); + on_each_cpu(rcu_barrier_func, NULL, 1); rcu_read_unlock(); wait_for_completion(&rcu_barrier_completion); mutex_unlock(&rcu_barrier_mutex); diff --git a/kernel/softirq.c b/kernel/softirq.c index d73afb4764e..c159fd09477 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -674,7 +674,7 @@ __init int spawn_ksoftirqd(void) /* * Call a function on all processors */ -int on_each_cpu(void (*func) (void *info), void *info, int retry, int wait) +int on_each_cpu(void (*func) (void *info), void *info, int wait) { int ret = 0; -- cgit v1.2.3 From ce0d1b6f73870878aae622b72e85fe8f7a16b51c Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Fri, 27 Jun 2008 11:50:32 +0200 Subject: fix: "smp_call_function: get rid of the unused nonatomic/retry argument" fix: kernel/smp.c: In function 'smp_call_function_mask': kernel/smp.c:303: error: too many arguments to function 'smp_call_function_single' Signed-off-by: Ingo Molnar --- kernel/smp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/smp.c b/kernel/smp.c index 7e0432a4a0e..4f582b257eb 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -300,7 +300,7 @@ int smp_call_function_mask(cpumask_t mask, void (*func)(void *), void *info, return 0; else if (num_cpus == 1) { cpu = first_cpu(mask); - return smp_call_function_single(cpu, func, info, 0, wait); + return smp_call_function_single(cpu, func, info, wait); } if (!wait) { -- cgit v1.2.3