Impact: Implementation change to remove cpumask_t from stack. Actually change smp_call_function_mask() to smp_call_function_many(). We avoid cpumasks on the stack in this version. (S390 has its own version, but that's going away apparently). We have to do some dancing to figure out if 0 or 1 other cpus are in the mask supplied and the online mask without allocating a tmp cpumask. It's still fairly cheap. We allocate the cpumask at the end of the call_function_data structure: if allocation fails we fallback to smp_call_function_single rather than using the baroque quiescing code (which needs a cpumask on stack). (Thanks to Hiroshi Shimamoto for spotting several bugs in previous versions!) Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Cc: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Cc: npiggin@suse.de Cc: axboe@kernel.dk
396 lines
9.9 KiB
C
396 lines
9.9 KiB
C
/*
|
|
* 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,
|
|
};
|
|
|
|
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_ALLOC)
|
|
kfree(data);
|
|
}
|
|
/*
|
|
* See comment on outer loop
|
|
*/
|
|
smp_read_barrier_depends();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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_CPUS && cpu_online(cpu)) {
|
|
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);
|
|
} 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);
|
|
}
|
|
|
|
/**
|
|
* 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(*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);
|
|
}
|