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workqueue: simplify CPU hotplug code 

With trustee gone, CPU hotplug code can be simplified.

* gcwq_claim/release_management() now grab and release gcwq lock too
  respectively and gained _and_lock and _and_unlock postfixes.

* All CPU hotplug logic was implemented in workqueue_cpu_callback()
  which was called by workqueue_cpu_up/down_callback() for the correct
  priority.  This was because up and down paths shared a lot of logic,
  which is no longer true.  Remove workqueue_cpu_callback() and move
  all hotplug logic into the two actual callbacks.

This patch doesn't make any functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: "Rafael J. Wysocki" <rjw@sisk.pl>
This commit is contained in:
Tejun Heo 2012-07-17 12:39:28 -07:00
parent 628c78e7ea
commit 8db25e7891
1 changed files with 27 additions and 56 deletions
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83
kernel/workqueue.c
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@ -3358,19 +3358,21 @@ EXPORT_SYMBOL_GPL(work_busy);
*/
/* claim manager positions of all pools */
static void gcwq_claim_management(struct global_cwq *gcwq)
static void gcwq_claim_management_and_lock(struct global_cwq *gcwq)
{
struct worker_pool *pool;
for_each_worker_pool(pool, gcwq)
mutex_lock_nested(&pool->manager_mutex, pool - gcwq->pools);
spin_lock_irq(&gcwq->lock);
}
/* release manager positions */
static void gcwq_release_management(struct global_cwq *gcwq)
static void gcwq_release_management_and_unlock(struct global_cwq *gcwq)
{
struct worker_pool *pool;
spin_unlock_irq(&gcwq->lock);
for_each_worker_pool(pool, gcwq)
mutex_unlock(&pool->manager_mutex);
}
@ -3385,8 +3387,7 @@ static void gcwq_unbind_fn(struct work_struct *work)
BUG_ON(gcwq->cpu != smp_processor_id());
gcwq_claim_management(gcwq);
spin_lock_irq(&gcwq->lock);
gcwq_claim_management_and_lock(gcwq);
/*
* We've claimed all manager positions. Make all workers unbound
@ -3403,8 +3404,7 @@ static void gcwq_unbind_fn(struct work_struct *work)
gcwq->flags |= GCWQ_DISASSOCIATED;
spin_unlock_irq(&gcwq->lock);
gcwq_release_management(gcwq);
gcwq_release_management_and_unlock(gcwq);
/*
* Call schedule() so that we cross rq->lock and thus can guarantee
@ -3428,26 +3428,19 @@ static void gcwq_unbind_fn(struct work_struct *work)
atomic_set(get_pool_nr_running(pool), 0);
}
static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
/*
* Workqueues should be brought up before normal priority CPU notifiers.
* This will be registered high priority CPU notifier.
*/
static int __devinit workqueue_cpu_up_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
struct global_cwq *gcwq = get_gcwq(cpu);
struct worker_pool *pool;
struct work_struct unbind_work;
unsigned long flags;
action &= ~CPU_TASKS_FROZEN;
switch (action) {
case CPU_DOWN_PREPARE:
/* unbinding should happen on the local CPU */
INIT_WORK_ONSTACK(&unbind_work, gcwq_unbind_fn);
schedule_work_on(cpu, &unbind_work);
flush_work(&unbind_work);
break;
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_UP_PREPARE:
for_each_worker_pool(pool, gcwq) {
struct worker *worker;
@ -3463,44 +3456,15 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
start_worker(worker);
spin_unlock_irq(&gcwq->lock);
}
}
/* some are called w/ irq disabled, don't disturb irq status */
spin_lock_irqsave(&gcwq->lock, flags);
switch (action) {
case CPU_DOWN_FAILED:
case CPU_ONLINE:
spin_unlock_irq(&gcwq->lock);
gcwq_claim_management(gcwq);
spin_lock_irq(&gcwq->lock);
gcwq->flags &= ~GCWQ_DISASSOCIATED;
rebind_workers(gcwq);
gcwq_release_management(gcwq);
break;
}
spin_unlock_irqrestore(&gcwq->lock, flags);
return notifier_from_errno(0);
}
/*
* Workqueues should be brought up before normal priority CPU notifiers.
* This will be registered high priority CPU notifier.
*/
static int __devinit workqueue_cpu_up_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
{
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_UP_PREPARE:
case CPU_DOWN_FAILED:
case CPU_ONLINE:
return workqueue_cpu_callback(nfb, action, hcpu);
gcwq_claim_management_and_lock(gcwq);
gcwq->flags &= ~GCWQ_DISASSOCIATED;
rebind_workers(gcwq);
gcwq_release_management_and_unlock(gcwq);
break;
}
return NOTIFY_OK;
}
@ -3513,9 +3477,16 @@ static int __devinit workqueue_cpu_down_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
struct work_struct unbind_work;
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_PREPARE:
return workqueue_cpu_callback(nfb, action, hcpu);
/* unbinding should happen on the local CPU */
INIT_WORK_ONSTACK(&unbind_work, gcwq_unbind_fn);
schedule_work_on(cpu, &unbind_work);
flush_work(&unbind_work);
break;
}
return NOTIFY_OK;
}