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generic-ipi: remove CSD_FLAG_WAIT

Browse source 
Oleg noticed that we don't strictly need CSD_FLAG_WAIT, rework
the code so that we can use CSD_FLAG_LOCK for both purposes.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-02-25 13:59:48 +01:00 committed by Ingo Molnar
parent 8969a5ede0
commit 6e2756376c
5 changed files with 29 additions and 72 deletions
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2
block/blk-softirq.c
View file

@ -64,7 +64,7 @@ static int raise_blk_irq(int cpu, struct request *rq)
data->info = rq;
data->flags = 0;
__smp_call_function_single(cpu, data);
__smp_call_function_single(cpu, data, 0);
return 0;
}

3
include/linux/smp.h
View file

@ -82,7 +82,8 @@ smp_call_function_mask(cpumask_t mask, void(*func)(void *info), void *info,
return 0;
}
void __smp_call_function_single(int cpuid, struct call_single_data *data);
void __smp_call_function_single(int cpuid, struct call_single_data *data,
int wait);
/*
* Generic and arch helpers

2
kernel/sched.c
View file

@ -1093,7 +1093,7 @@ static void hrtick_start(struct rq *rq, u64 delay)
if (rq == this_rq()) {
hrtimer_restart(timer);
} else if (!rq->hrtick_csd_pending) {
__smp_call_function_single(cpu_of(rq), &rq->hrtick_csd);
__smp_call_function_single(cpu_of(rq), &rq->hrtick_csd, 0);
rq->hrtick_csd_pending = 1;
}
}

92
kernel/smp.c
View file

@ -23,8 +23,7 @@ static struct {
};
enum {
CSD_FLAG_WAIT = 0x01,
CSD_FLAG_LOCK = 0x02,
CSD_FLAG_LOCK = 0x01,
};
struct call_function_data {
@ -94,31 +93,6 @@ static int __cpuinit init_call_single_data(void)
}
early_initcall(init_call_single_data);
/*
* csd_wait/csd_complete are used for synchronous ipi calls
*/
static void csd_wait_prepare(struct call_single_data *data)
{
data->flags |= CSD_FLAG_WAIT;
}
static void csd_complete(struct call_single_data *data)
{
if (data->flags & CSD_FLAG_WAIT) {
/*
* ensure we're all done before saying we are
*/
smp_mb();
data->flags &= ~CSD_FLAG_WAIT;
}
}
static void csd_wait(struct call_single_data *data)
{
while (data->flags & CSD_FLAG_WAIT)
cpu_relax();
}
/*
* csd_lock/csd_unlock used to serialize access to per-cpu csd resources
*
@ -126,10 +100,15 @@ static void csd_wait(struct call_single_data *data)
* 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(struct call_single_data *data)
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;
/*
@ -155,11 +134,12 @@ static void csd_unlock(struct call_single_data *data)
* 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);
@ -182,7 +162,7 @@ static void generic_exec_single(int cpu, struct call_single_data *data)
arch_send_call_function_single_ipi(cpu);
if (wait)
csd_wait(data);
csd_lock_wait(data);
}
/*
@ -232,7 +212,6 @@ void generic_smp_call_function_interrupt(void)
if (refs)
continue;
csd_complete(&data->csd);
csd_unlock(&data->csd);
}
@ -270,9 +249,6 @@ void generic_smp_call_function_single_interrupt(void)
data->func(data->info);
if (data_flags & CSD_FLAG_WAIT)
csd_complete(data);
/*
* Unlocked CSDs are valid through generic_exec_single()
*/
@ -313,36 +289,16 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
func(info);
local_irq_restore(flags);
} else if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
struct call_single_data *data;
struct call_single_data *data = &d;
if (!wait) {
/*
* We are calling a function on a single CPU
* and we are not going to wait for it to finish.
* We 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.
*/
if (!wait)
data = &__get_cpu_var(csd_data);
csd_lock(data);
} else {
data = &d;
csd_wait_prepare(data);
}
csd_lock(data);
data->func = func;
data->info = info;
generic_exec_single(cpu, data);
generic_exec_single(cpu, data, wait);
} else {
err = -ENXIO; /* CPU not online */
}
@ -362,12 +318,15 @@ EXPORT_SYMBOL(smp_call_function_single);
* 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)
{
/* Can deadlock when called with interrupts disabled */
WARN_ON((data->flags & CSD_FLAG_WAIT) && irqs_disabled());
csd_lock(data);
generic_exec_single(cpu, data);
/* Can deadlock when called with interrupts disabled */
WARN_ON(wait && irqs_disabled());
generic_exec_single(cpu, data, wait);
}
/* FIXME: Shim for archs using old arch_send_call_function_ipi API. */
@ -425,9 +384,6 @@ void smp_call_function_many(const struct cpumask *mask,
csd_lock(&data->csd);
spin_lock_irqsave(&data->lock, flags);
if (wait)
csd_wait_prepare(&data->csd);
data->csd.func = func;
data->csd.info = info;
cpumask_and(data->cpumask, mask, cpu_online_mask);
@ -456,7 +412,7 @@ void smp_call_function_many(const struct cpumask *mask,
/* optionally wait for the CPUs to complete */
if (wait)
csd_wait(&data->csd);
csd_lock_wait(&data->csd);
}
EXPORT_SYMBOL(smp_call_function_many);

2
kernel/softirq.c
View file

@ -496,7 +496,7 @@ static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softir
cp->flags = 0;
cp->priv = softirq;
__smp_call_function_single(cpu, cp);
__smp_call_function_single(cpu, cp, 0);
return 0;
}
return 1;