From 83c22520c51bf67529367e8237f95c03fe44e2da Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 9 May 2007 02:33:54 -0700 Subject: [PATCH] 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 Cc: Srivatsa Vaddagiri Cc: Gautham Shenoy Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/workqueue.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 5176d51bcc2a..5ecf4984e382 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -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); -- 2.20.1