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/*
* Generic helpers for smp ipi calls
*
* (C) Jens Axboe <jens.axboe@oracle.com> 2008
*/
#include <linux/rcupdate.h>
#include <linux/rculist.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/cpu.h>
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),
};
enum {
CSD_FLAG_LOCK = 0x01,
};
struct call_function_data {
struct call_single_data csd;
atomic_t refs;
cpumask_var_t cpumask;
};
struct call_single_queue {
struct list_head list;
spinlock_t lock;
};
static DEFINE_PER_CPU(struct call_function_data, cfd_data);
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 (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
cpu_to_node(cpu)))
return NOTIFY_BAD;
break;
#ifdef CONFIG_HOTPLUG_CPU
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) {
struct call_single_queue *q = &per_cpu(call_single_queue, i);
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);
/*
* 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_wait(struct call_single_data *data)
{
while (data->flags & CSD_FLAG_LOCK)
cpu_relax();
}
static void csd_lock(struct call_single_data *data)
{
csd_lock_wait(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:
*/
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;
}
/*
* 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)
{
struct call_single_queue *dst = &per_cpu(call_single_queue, cpu);
unsigned long flags;
int ipi;
spin_lock_irqsave(&dst->lock, flags);
ipi = list_empty(&dst->list);
list_add_tail(&data->list, &dst->list);
spin_unlock_irqrestore(&dst->lock, flags);
/*
* The list addition should be visible before sending the IPI
* handler locks the list to pull the entry off it because of
* normal cache coherency rules implied by spinlocks.
*
* 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...
*/
if (ipi)
arch_send_call_function_single_ipi(cpu);
if (wait)
csd_lock_wait(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();
/*
* Shouldn't receive this interrupt on a cpu that is not yet online.
*/
WARN_ON_ONCE(!cpu_online(cpu));
/*
* Ensure entry is visible on call_function_queue after we have
* entered the IPI. See comment in smp_call_function_many.
* If we don't have this, then we may miss an entry on the list
* and never get another IPI to process it.
*/
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
*/
list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
int refs;
if (!cpumask_test_and_clear_cpu(cpu, data->cpumask))
continue;
data->csd.func(data->csd.info);
refs = atomic_dec_return(&data->refs);
WARN_ON(refs < 0);
if (!refs) {
spin_lock(&call_function.lock);
list_del_rcu(&data->csd.list);
spin_unlock(&call_function.lock);
}
if (refs)
continue;
csd_unlock(&data->csd);
}
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);
unsigned int data_flags;
LIST_HEAD(list);
/*
* Shouldn't receive this interrupt on a cpu that is not yet online.
*/
WARN_ON_ONCE(!cpu_online(smp_processor_id()));
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);
/*
* Unlocked CSDs are valid through generic_exec_single():
*/
if (data_flags & CSD_FLAG_LOCK)
csd_unlock(data);
}
}
static DEFINE_PER_CPU(struct call_single_data, csd_data);
/*
* 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.
*/
int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
int wait)
{
struct call_single_data d = {
.flags = 0,
};
unsigned long flags;
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.
* We allow cpu's that are not yet online though, as no one else can
* send smp call function interrupt to this cpu and as such deadlocks
* can't happen.
*/
WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
&& !oops_in_progress);
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;
if (!wait)
data = &__get_cpu_var(csd_data);
csd_lock(data);
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);
/*
* smp_call_function_any - Run a function on any of the given cpus
* @mask: The mask of cpus it can 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 until function has completed.
*
* Returns 0 on success, else a negative status code (if no cpus were online).
* Note that @wait will be implicitly turned on in case of allocation failures,
* since we fall back to on-stack allocation.
*
* Selection preference:
* 1) current cpu if in @mask
* 2) any cpu of current node if in @mask
* 3) any other online cpu in @mask
*/
int smp_call_function_any(const struct cpumask *
|