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linux-aio: Cancel BH if not needed

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linux-aio uses a BH in order to make sure that the remaining completions
are processed even in nested event loops of completion callbacks in
order to avoid deadlocks.

There is no need, however, to have the BH overhead for the first call
into qemu_laio_completion_bh() or after all pending completions have
already been processed. Therefore, this patch calls directly into
qemu_laio_completion_bh() in qemu_laio_completion_cb() and cancels
the BH after qemu_laio_completion_bh() has processed all pending
completions.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Kevin Wolf 2014-11-28 15:23:12 +01:00
parent 23b0d9fb1d
commit ccb9dc1012
1 changed files with 3 additions and 1 deletions
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4
block/linux-aio.c
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@ -149,6 +149,8 @@ static void qemu_laio_completion_bh(void *opaque)
if (!s->io_q.plugged && !QSIMPLEQ_EMPTY(&s->io_q.pending)) {
ioq_submit(s);
}
qemu_bh_cancel(s->completion_bh);
}
static void qemu_laio_completion_cb(EventNotifier *e)
@ -156,7 +158,7 @@ static void qemu_laio_completion_cb(EventNotifier *e)
LinuxAioState *s = container_of(e, LinuxAioState, e);
if (event_notifier_test_and_clear(&s->e)) {
qemu_bh_schedule(s->completion_bh);
qemu_laio_completion_bh(s);
}
}