From 0b06ef3bdd17742ae50c0662d3fe8ed944648890 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Tue, 26 Nov 2013 16:18:00 +0100 Subject: block: clean up bdrv_drain_all() throttling comments Since cc0681c45430a1f1a4c2d06e9499b7775afc9a18 ("block: Enable the new throttling code in the block layer.") bdrv_drain_all() no longer spins. The code used to look as follows: do { busy = qemu_aio_wait(); /* FIXME: We do not have timer support here, so this is effectively * a busy wait. */ QTAILQ_FOREACH(bs, &bdrv_states, list) { while (qemu_co_enter_next(&bs->throttled_reqs)) { busy = true; } } } while (busy); Note that throttle requests are kicked but I/O throttling limits are still in effect. The loop spins until the vm_clock time allows the request to make progress and complete. The new throttling code introduced bdrv_start_throttled_reqs(). This function not only kicks throttled requests but also temporarily disables throttling so requests can run. The outdated FIXME comment can be removed. Also drop the busy = true assignment since we overwrite it immediately afterwards. Reviewed-by: Alex Bligh Signed-off-by: Stefan Hajnoczi --- block.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/block.c b/block.c index 1c83ef1fab..13f001ad69 100644 --- a/block.c +++ b/block.c @@ -1557,13 +1557,8 @@ void bdrv_drain_all(void) BlockDriverState *bs; while (busy) { - /* FIXME: We do not have timer support here, so this is effectively - * a busy wait. - */ QTAILQ_FOREACH(bs, &bdrv_states, list) { - if (bdrv_start_throttled_reqs(bs)) { - busy = true; - } + bdrv_start_throttled_reqs(bs); } busy = bdrv_requests_pending_all(); -- cgit v1.2.3