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Subject[PATCH 9/9] workqueue: simplify CPU hotplug code
Date
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>
---
kernel/workqueue.c | 79 ++++++++++++++++-----------------------------------
1 files changed, 25 insertions(+), 54 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index d1545da..471996a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -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;
@@ -3463,45 +3456,16 @@ 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);
+ break;

- switch (action) {
case CPU_DOWN_FAILED:
case CPU_ONLINE:
- spin_unlock_irq(&gcwq->lock);
- gcwq_claim_management(gcwq);
- spin_lock_irq(&gcwq->lock);
-
+ gcwq_claim_management_and_lock(gcwq);
gcwq->flags &= ~GCWQ_DISASSOCIATED;
-
rebind_workers(gcwq);
-
- gcwq_release_management(gcwq);
+ gcwq_release_management_and_unlock(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);
- }
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;
}
--
1.7.7.3


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