Thread (61 messages) 61 messages, 7 authors, 2011-04-20

Re: [PATCH 05/10] block: remove per-queue plugging

From: Peter Zijlstra <peterz@infradead.org>
Date: 2011-04-13 11:09:35
Also in: dm-devel, lkml

On Tue, 2011-04-12 at 19:23 -0700, Linus Torvalds wrote:
quoted hunk ↗ jump to hunk
 kernel/sched.c |   20 ++++++++++----------
 1 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index 48013633d792..a187c3fe027b 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4111,20 +4111,20 @@ need_resched:
                                        try_to_wake_up_local(to_wakeup);
                        }
                        deactivate_task(rq, prev, DEQUEUE_SLEEP);
+
+                       /*
+                        * If we are going to sleep and we have plugged IO queued, make
+                        * sure to submit it to avoid deadlocks.
+                        */
+                       if (blk_needs_flush_plug(prev)) {
+                               raw_spin_unlock(&rq->lock);
+                               blk_flush_plug(prev);
+                               raw_spin_lock(&rq->lock);
+                       }
                }
                switch_count = &prev->nvcsw;
        }
 
-       /*
-        * If we are going to sleep and we have plugged IO queued, make
-        * sure to submit it to avoid deadlocks.
-        */
-       if (prev->state != TASK_RUNNING && blk_needs_flush_plug(prev)) {
-               raw_spin_unlock(&rq->lock);
-               blk_flush_plug(prev);
-               raw_spin_lock(&rq->lock);
-       }
-
        pre_schedule(rq, prev);
 
        if (unlikely(!rq->nr_running)) 
Right, that cures the preemption problem. The reason I suggested placing
it where it was is that I'd like to keep all things that release
rq->lock in the middle of schedule() in one place, but I guess we can
cure that with some extra comments.
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