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 <[email protected]>
--- mm-6.20-rc3/kernel/workqueue.c~1_opt 2007-01-07 23:15:50.000000000 +0300
+++ mm-6.20-rc3/kernel/workqueue.c 2007-01-07 23:26:45.000000000 +0300
@@ -405,12 +405,15 @@ static void wq_barrier_func(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)
@@ -429,13 +432,20 @@ static void flush_cpu_workqueue(struct c
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();
+ }
}
}
@@ -482,8 +492,7 @@ static void wait_on_work(struct cpu_work
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);
-
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