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generic-ipi: cleanups
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Andrew pointed out that there's some small amount of
style rot in kernel/smp.c.

Clean it up.

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Ingo Molnar committed Feb 25, 2009
1 parent 6e27563 commit 0b13fda
Showing 1 changed file with 86 additions and 76 deletions.
162 changes: 86 additions & 76 deletions kernel/smp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2,13 +2,12 @@
* 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/module.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/cpu.h>

Expand All @@ -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
Expand Down Expand Up @@ -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)
Expand All @@ -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)
{
Expand All @@ -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)
Expand All @@ -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);

Expand All @@ -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;
Expand Down Expand Up @@ -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);
Expand All @@ -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);
Expand All @@ -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);
Expand All @@ -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)
Expand All @@ -329,18 +334,20 @@ 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

/**
* 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.
* @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
Expand All @@ -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. */
Expand All @@ -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);
}
Expand All @@ -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.
*
Expand All @@ -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);
Expand Down

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