Messages in this thread Patch in this message | | | Date | Tue, 22 Apr 2008 20:23:38 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH 1/11] Add generic helpers for arch IPI function calls |
| |
On Tue, Apr 22 2008, Linus Torvalds wrote: > > > On Tue, 22 Apr 2008, Jens Axboe wrote: > > > > But wait, falling back to wait cannot always be safe if we are called > > with interrupts disabled. I don't see any way around using the global > > fallback for that case. > > Hmm. Good point. It does look like you need three cases.
OK, so how about this then? All three cases for both smp_call_function_single() and smp_call_function_mask(). Data is always freed in the ipi interrupt handler, since the 'wait' case is always allocated on the stack.
From 98cafbfd86760ccd3b0498b83b5b9ca044534b04 Mon Sep 17 00:00:00 2001 From: Jens Axboe <jens.axboe@oracle.com> Date: Tue, 22 Apr 2008 20:14:09 +0200 Subject: [PATCH] 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" <Alan.Brunelle@hp.com> has contributed lots of fixes and suggestions as well.
Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Jens Axboe <jens.axboe@oracle.com> --- arch/Kconfig | 3 + include/linux/smp.h | 27 ++++- init/main.c | 3 + kernel/Makefile | 1 + kernel/smp.c | 366 +++++++++++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 398 insertions(+), 2 deletions(-) create mode 100644 kernel/smp.c
diff --git a/arch/Kconfig b/arch/Kconfig index 694c9af..a5a0184 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -36,3 +36,6 @@ config HAVE_KPROBES config HAVE_KRETPROBES def_bool n + +config USE_GENERIC_SMP_HELPERS + def_bool n diff --git a/include/linux/smp.h b/include/linux/smp.h index 55232cc..4a5418b 100644 --- a/include/linux/smp.h +++ b/include/linux/smp.h @@ -7,9 +7,19 @@ */ #include <linux/errno.h> +#include <linux/list.h> +#include <linux/spinlock.h> +#include <linux/cpumask.h> extern void cpu_idle(void); +struct call_single_data { + struct list_head list; + void (*func) (void *info); + void *info; + unsigned int flags; +}; + #ifdef CONFIG_SMP #include <linux/preempt.h> @@ -53,9 +63,23 @@ extern void smp_cpus_done(unsigned int max_cpus); * Call a function on all other processors */ int smp_call_function(void(*func)(void *info), void *info, int retry, int wait); - +int smp_call_function_mask(cpumask_t mask, void(*func)(void *info), void *info, + int wait); int smp_call_function_single(int cpuid, void (*func) (void *info), void *info, int retry, int wait); +void __smp_call_function_single(int cpuid, struct call_single_data *data); + +/* + * Generic and arch helpers + */ +#ifdef CONFIG_USE_GENERIC_SMP_HELPERS +void generic_smp_call_function_single_interrupt(void); +void generic_smp_call_function_interrupt(void); +void init_call_single_data(void); +void arch_send_call_function_single_ipi(int cpu); +void arch_send_call_function_ipi(cpumask_t mask); +extern spinlock_t call_function_lock; +#endif /* * Call a function on all processors @@ -112,7 +136,6 @@ static inline void smp_send_reschedule(int cpu) { } }) #define smp_call_function_mask(mask, func, info, wait) \ (up_smp_call_function(func, info)) - #endif /* !SMP */ /* diff --git a/init/main.c b/init/main.c index 833a67d..0b7578c 100644 --- a/init/main.c +++ b/init/main.c @@ -773,6 +773,9 @@ static void __init do_pre_smp_initcalls(void) { extern int spawn_ksoftirqd(void); +#ifdef CONFIG_USE_GENERIC_SMP_HELPERS + init_call_single_data(); +#endif migration_init(); spawn_ksoftirqd(); if (!nosoftlockup) diff --git a/kernel/Makefile b/kernel/Makefile index 6c5f081..7e275d4 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 0000000..a177a0d --- /dev/null +++ b/kernel/smp.c @@ -0,0 +1,366 @@ +/* + * 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/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_FALLBACK = 0x04, +}; + +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; +}; + +static struct call_function_data cfd_fallback; +static unsigned long cfd_fallback_used; + +void __cpuinit init_call_single_data(void) +{ + int i; + + for_each_cpu_mask(i, cpu_possible_map) { + struct call_single_queue *q = &per_cpu(call_single_queue, i); + + spin_lock_init(&q->lock); + INIT_LIST_HEAD(&q->list); + } +} + +static inline 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 *cfd; + + cfd = container_of(head, struct call_function_data, rcu_head); + kfree(cfd); +} + +static void call_func_data_free(struct call_function_data *data) +{ + if (data->csd.flags & CSD_FLAG_ALLOC) + call_rcu(&data->rcu_head, rcu_free_call_data); + else + clear_bit_unlock(0, &cfd_fallback_used); +} + +/* + * Invoked by arch to handle an IPI for call function. Must be called with + * interrupts disabled. + */ +void generic_smp_call_function_interrupt(void) +{ + struct list_head *pos; + 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_rcu(pos, &call_function_queue) { + struct call_function_data *data; + int refs; + + data = list_entry(pos, struct call_function_data, csd.list); + 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; + + WARN_ON(cpus_weight(data->cpumask)); + spin_lock(&call_function_lock); + list_del_rcu(&data->csd.list); + spin_unlock(&call_function_lock); + + if (data->csd.flags & CSD_FLAG_WAIT) { + smp_wmb(); + data->csd.flags &= ~CSD_FLAG_WAIT; + } else + call_func_data_free(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); + + 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); + else if (data_flags & CSD_FLAG_FALLBACK) + clear_bit_unlock(0, &cfd_fallback_used); + } + 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. + * + */ +int smp_call_function_single(int cpu, void (*func) (void *info), void *info, + int retry, int wait) +{ + unsigned long flags; + /* prevent preemption and reschedule on another processor */ + int me = get_cpu(); + + /* Can deadlock when called with interrupts disabled */ + WARN_ON(wait && irqs_disabled()); + + if (cpu == me) { + local_irq_save(flags); + func(info); + local_irq_restore(flags); + } else { + struct call_single_data *data; + + if (wait) { + struct call_single_data d; + + data = &d; + data->flags = CSD_FLAG_WAIT; + } else { + data = kmalloc(sizeof(*data), GFP_ATOMIC); + if (data) + data->flags = CSD_FLAG_ALLOC; + else { + while (test_and_set_bit_lock(0, + &cfd_fallback_used)) + cpu_relax(); + + data = &cfd_fallback.csd; + data->flags = CSD_FLAG_FALLBACK; + } + } + + 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) +{ + 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. + * + * 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_mask(cpumask_t mask, void (*func)(void *), void *info, + int wait) +{ + struct call_function_data *data; + cpumask_t allbutself; + unsigned long flags; + int num_cpus; + + /* Can deadlock when called with interrupts disabled */ + WARN_ON(wait && irqs_disabled()); + + allbutself = cpu_online_map; + cpu_clear(smp_processor_id(), allbutself); + cpus_and(mask, mask, allbutself); + num_cpus = cpus_weight(mask); + + if (!num_cpus) + return 0; + + if (wait) { + struct call_function_data d; + + data = &d; + data->csd.flags = CSD_FLAG_WAIT; + } else { + data = kmalloc(sizeof(*data), GFP_ATOMIC); + if (data) + data->csd.flags = CSD_FLAG_ALLOC; + else { + while (test_and_set_bit_lock(0, &cfd_fallback_used)) + cpu_relax(); + + data = &cfd_fallback; + data->csd.flags = CSD_FLAG_FALLBACK; + } + } + + 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. + * + * 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); -- 1.5.5.1.57.g5909c -- Jens Axboe
| |