Author: Ingo Molnar <mingo@xxxxxxx>
AuthorDate: Wed, 25 Feb 2009 16:52:11 +0100
Commit: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Wed, 25 Feb 2009 16:52:50 +0100
generic-ipi: cleanups
Andrew pointed out that there's some small amount of
style rot in kernel/smp.c.
Clean it up.
Reported-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxx>
Cc: Jens Axboe <jens.axboe@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/smp.c | 162 +++++++++++++++++++++++++++++++---------------------------
1 files changed, 86 insertions(+), 76 deletions(-)
diff --git a/kernel/smp.c b/kernel/smp.c
index f530825..7ad2262 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -2,13 +2,12 @@
* Generic helpers for smp ipi calls
*
* (C) Jens Axboe <jens.axboe@xxxxxxxxxx> 2008
- *
*/
-#include <linux/init.h>
-#include <linux/module.h>
-#include <linux/percpu.h>
#include <linux/rcupdate.h>
#include <linux/rculist.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
#include <linux/smp.h>
#include <linux/cpu.h>
@@ -17,29 +16,30 @@ 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),
-};
+} 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;
- spinlock_t lock;
- unsigned int refs;
- cpumask_var_t cpumask;
+ 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),
+ .lock = __SPIN_LOCK_UNLOCKED(cfd_data.lock),
};
static int
@@ -71,7 +71,7 @@ hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
}
static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
- .notifier_call = hotplug_cfd,
+ .notifier_call = hotplug_cfd,
};
static int __cpuinit init_call_single_data(void)
@@ -96,9 +96,9 @@ 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.
+ * 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)
{
@@ -112,27 +112,29 @@ static void csd_lock(struct call_single_data *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.
+ * 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
+ * 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, int wait)
@@ -154,10 +156,9 @@ void generic_exec_single(int cpu, struct call_single_data *data, int wait)
* 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...
+ * locking and barrier primitives. Generic code isn't really
+ * equipped to do the right thing...
*/
-
if (ipi)
arch_send_call_function_single_ipi(cpu);
@@ -183,8 +184,8 @@ void generic_smp_call_function_interrupt(void)
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
+ * 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;
@@ -219,14 +220,14 @@ void generic_smp_call_function_interrupt(void)
}
/*
- * 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);
- LIST_HEAD(list);
unsigned int data_flags;
+ LIST_HEAD(list);
spin_lock(&q->lock);
list_replace_init(&q->list, &list);
@@ -235,22 +236,20 @@ void generic_smp_call_function_single_interrupt(void)
while (!list_empty(&list)) {
struct call_single_data *data;
- data = list_entry(list.next, struct call_single_data,
- list);
+ 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' 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()
+ * Unlocked CSDs are valid through generic_exec_single():
*/
if (data_flags & CSD_FLAG_LOCK)
csd_unlock(data);
@@ -276,34 +275,41 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
.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());
- 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 = &d;
+ } 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)
+ data = &__get_cpu_var(csd_data);
- csd_lock(data);
+ csd_lock(data);
- data->func = func;
- data->info = info;
- generic_exec_single(cpu, data, wait);
- } else {
- err = -ENXIO; /* CPU not online */
+ 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);
@@ -313,10 +319,9 @@ 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,
int wait)
@@ -329,10 +334,11 @@ void __smp_call_function_single(int cpu, struct call_single_data *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
/**
@@ -340,7 +346,8 @@ void __smp_call_function_single(int cpu, struct call_single_data *data,
* @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
@@ -351,27 +358,27 @@ void __smp_call_function_single(int cpu, struct call_single_data *data,
* 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, me = smp_processor_id();
+ int cpu, next_cpu, this_cpu = smp_processor_id();
/* Can deadlock when called with interrupts disabled */
WARN_ON(irqs_disabled());
- /* 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 == me)
+ 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 == me)
+ if (next_cpu == this_cpu)
next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
/* Fastpath: do that cpu by itself. */
@@ -387,30 +394,31 @@ void smp_call_function_many(const struct cpumask *mask,
data->csd.func = func;
data->csd.info = info;
cpumask_and(data->cpumask, mask, cpu_online_mask);
- cpumask_clear_cpu(me, data->cpumask);
+ cpumask_clear_cpu(this_cpu, data->cpumask);
data->refs = cpumask_weight(data->cpumask);
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.
+ * 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).
+ * (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(data->cpumask);
- /* optionally wait for the CPUs to complete */
+ /* Optionally wait for the CPUs to complete */
if (wait)
csd_lock_wait(&data->csd);
}
@@ -420,7 +428,8 @@ 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.
*
@@ -436,6 +445,7 @@ 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);
--
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