* 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/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 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 = 0x01,
};
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_data csd;
+ spinlock_t lock;
+ unsigned int refs;
+ cpumask_var_t cpumask;
};
struct call_single_queue {
- struct list_head list;
- spinlock_t lock;
+ struct list_head list;
+ 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 (!zalloc_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) {
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_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)
{
- /* Wait for response */
- do {
- if (!(data->flags & CSD_FLAG_WAIT))
- break;
+ while (data->flags & CSD_FLAG_LOCK)
cpu_relax();
- } while (1);
+}
+
+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.
+ * 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)
+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);
- int wait = data->flags & CSD_FLAG_WAIT, ipi;
unsigned long flags;
+ int ipi;
spin_lock_irqsave(&dst->lock, flags);
ipi = list_empty(&dst->list);
spin_unlock_irqrestore(&dst->lock, flags);
/*
- * Make the list addition visible before sending the ipi.
+ * 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...
*/
- 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);
+ csd_lock_wait(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
+ * 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
*/
- 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_unlock(&data->csd);
}
- 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.
+ * 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);
- /*
- * 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_LOCK) {
- smp_wmb();
- data->flags &= ~CSD_FLAG_LOCK;
- } else if (data_flags & CSD_FLAG_ALLOC)
- kfree(data);
- }
+ 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);
+
/*
- * See comment on outer loop
+ * Unlocked CSDs are valid through generic_exec_single():
*/
- smp_read_barrier_depends();
+ if (data_flags & CSD_FLAG_LOCK)
+ csd_unlock(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 */
- int me = get_cpu();
+ 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 */
- WARN_ON(irqs_disabled());
+ WARN_ON_ONCE(irqs_disabled() && !oops_in_progress);
- if (cpu == me) {
+ 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;
+ } else {
+ if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
+ struct call_single_data *data = &d;
+
+ if (!wait)
+ data = &__get_cpu_var(csd_data);
- if (!wait) {
- /*
- * 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.
- *
- * The CSD_FLAG_LOCK is used to let us know when
- * the IPI handler is done with the data.
- * The first caller will set it, and the callee
- * will clear it. The next caller must wait for
- * it to clear before we set it again. This
- * 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;
- }
+ csd_lock(data);
+
+ data->func = func;
+ data->info = info;
+ generic_exec_single(cpu, data, wait);
} else {
- data = &d;
- data->flags = CSD_FLAG_WAIT;
+ err = -ENXIO; /* CPU not online */
}
-
- 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);
* @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.
- *
+ * 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)
+void __smp_call_function_single(int cpu, struct call_single_data *data,
+ int wait)
{
+ csd_lock(data);
+
/* Can deadlock when called with interrupts disabled */
- WARN_ON((data->flags & CSD_FLAG_WAIT) && irqs_disabled());
+ WARN_ON_ONCE(wait && irqs_disabled() && !oops_in_progress);
- generic_exec_single(cpu, data);
+ generic_exec_single(cpu, data, wait);
}
-/* FIXME: Shim for archs using old arch_send_call_function_ipi API. */
+/* Deprecated: shim for archs using old arch_send_call_function_ipi API. */
+
#ifndef arch_send_call_function_ipi_mask
-#define arch_send_call_function_ipi_mask(maskp) \
- arch_send_call_function_ipi(*(maskp))
+# define arch_send_call_function_ipi_mask(maskp) \
+ arch_send_call_function_ipi(*(maskp))
#endif
/**
* @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.
+ * @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
* must be disabled when calling this function.
*/
void smp_call_function_many(const struct cpumask *mask,
- void (*func)(void *), void *info,
- bool wait)
+ void (*func)(void *), void *info, bool wait)
{
struct call_function_data *data;
unsigned long flags;
- int cpu, next_cpu;
+ int cpu, next_cpu, this_cpu = smp_processor_id();
/* Can deadlock when called with interrupts disabled */
- WARN_ON(irqs_disabled());
+ WARN_ON_ONCE(irqs_disabled() && !oops_in_progress);
- /* So, what's a CPU they want? Ignoring this one. */
+ /* 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 == this_cpu)
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())
+ if (next_cpu == this_cpu)
next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
/* Fastpath: do that cpu by itself. */
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;
- if (wait)
- data->csd.flags |= CSD_FLAG_WAIT;
+ spin_lock_irqsave(&data->lock, flags);
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(this_cpu, 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.
+ * (IPIs must obey or appear to obey normal Linux cache
+ * coherency rules -- see comment in generic_exec_single).
*/
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 */
+ /* Optionally wait for the CPUs to complete */
if (wait)
- csd_flag_wait(&data->csd);
+ csd_lock_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.
+ * @wait: If true, wait (atomically) until function has completed
+ * on other CPUs.
*
* Returns 0.
*
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);
+ 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);
}
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff