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flush_cpu_workqueue: don't flush an empty ->worklist 

Now when we have ->current_work we can avoid adding a barrier and waiting
for its completition when cwq's queue is empty.

Note: this change is also useful if we change flush_workqueue() to also
check the dead CPUs.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Gautham Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2007-05-09 02:33:54 -07:00 committed by Linus Torvalds
parent edab2516a6
commit 83c22520c5
1 changed files with 17 additions and 8 deletions
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25
kernel/workqueue.c
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@ -404,12 +404,15 @@ static void wq_barrier_func(struct work_struct *work)
complete(&barr->done);
}
static inline void init_wq_barrier(struct wq_barrier *barr)
static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
struct wq_barrier *barr, int tail)
{
INIT_WORK(&barr->work, wq_barrier_func);
__set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
init_completion(&barr->done);
insert_work(cwq, &barr->work, tail);
}
static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
@ -428,13 +431,20 @@ static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
preempt_disable();
} else {
struct wq_barrier barr;
int active = 0;
init_wq_barrier(&barr);
__queue_work(cwq, &barr.work);
spin_lock_irq(&cwq->lock);
if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
insert_wq_barrier(cwq, &barr, 1);
active = 1;
}
spin_unlock_irq(&cwq->lock);
preempt_enable(); /* Can no longer touch *cwq */
wait_for_completion(&barr.done);
preempt_disable();
if (active) {
preempt_enable();
wait_for_completion(&barr.done);
preempt_disable();
}
}
}
@ -475,8 +485,7 @@ static void wait_on_work(struct cpu_workqueue_struct *cwq,
spin_lock_irq(&cwq->lock);
if (unlikely(cwq->current_work == work)) {
init_wq_barrier(&barr);
insert_work(cwq, &barr.work, 0);
insert_wq_barrier(cwq, &barr, 0);
running = 1;
}
spin_unlock_irq(&cwq->lock);