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[Qemu-block] [PATCH v3 2/4] block: use BDRV_POLL_WHILE() in bdrv_rw_vmst

From: Stefan Hajnoczi
Subject: [Qemu-block] [PATCH v3 2/4] block: use BDRV_POLL_WHILE() in bdrv_rw_vmstate()
Date: Mon, 22 May 2017 14:57:02 +0100

Calling aio_poll() directly may have been fine previously, but this is
the future, man!  The difference between an aio_poll() loop and
BDRV_POLL_WHILE() is that BDRV_POLL_WHILE() releases the AioContext
around aio_poll().

This allows the IOThread to run fd handlers or BHs to complete the
request.  Failure to release the AioContext causes deadlocks.

Using BDRV_POLL_WHILE() partially fixes a 'savevm' hang with -object

Signed-off-by: Stefan Hajnoczi <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Paolo Bonzini <address@hidden>
 block/io.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/block/io.c b/block/io.c
index cc56e90..f0041cd 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2031,9 +2031,7 @@ bdrv_rw_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, 
int64_t pos,
         Coroutine *co = qemu_coroutine_create(bdrv_co_rw_vmstate_entry, &data);
         bdrv_coroutine_enter(bs, co);
-        while (data.ret == -EINPROGRESS) {
-            aio_poll(bdrv_get_aio_context(bs), true);
-        }
+        BDRV_POLL_WHILE(bs, data.ret == -EINPROGRESS);
         return data.ret;

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