From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51719) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eMaxh-00070u-4K for qemu-devel@nongnu.org; Wed, 06 Dec 2017 09:46:16 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eMaxg-0003Dm-85 for qemu-devel@nongnu.org; Wed, 06 Dec 2017 09:46:13 -0500 From: Stefan Hajnoczi Date: Wed, 6 Dec 2017 14:45:42 +0000 Message-Id: <20171206144550.22295-2-stefanha@redhat.com> In-Reply-To: <20171206144550.22295-1-stefanha@redhat.com> References: <20171206144550.22295-1-stefanha@redhat.com> Subject: [Qemu-devel] [PATCH v2 1/9] blockdev: hold AioContext for bdrv_unref() in external_snapshot_clean() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, John Snow , Kevin Wolf , Stefan Hajnoczi bdrv_unref() requires the AioContext lock because bdrv_flush() uses BDRV_POLL_WHILE(), which assumes the AioContext is currently held. If BDRV_POLL_WHILE() runs without AioContext held the pthread_mutex_unlock() call in aio_context_release() fails. This patch moves bdrv_unref() into the AioContext locked region to solve the following pthread_mutex_unlock() failure: #0 0x00007f566181969b in raise () at /lib64/libc.so.6 #1 0x00007f566181b3b1 in abort () at /lib64/libc.so.6 #2 0x00005592cd590458 in error_exit (err=, msg=msg@entry=0x5592cdaf6d60 <__func__.23977> "qemu_mutex_unlock") at util/qemu-thread-posix.c:36 #3 0x00005592cd96e738 in qemu_mutex_unlock (mutex=mutex@entry=0x5592ce9505e0) at util/qemu-thread-posix.c:96 #4 0x00005592cd969b69 in aio_context_release (ctx=ctx@entry=0x5592ce950580) at util/async.c:507 #5 0x00005592cd8ead78 in bdrv_flush (bs=bs@entry=0x5592cfa87210) at block/io.c:2478 #6 0x00005592cd89df30 in bdrv_close (bs=0x5592cfa87210) at block.c:3207 #7 0x00005592cd89df30 in bdrv_delete (bs=0x5592cfa87210) at block.c:3395 #8 0x00005592cd89df30 in bdrv_unref (bs=0x5592cfa87210) at block.c:4418 #9 0x00005592cd6b7f86 in qmp_transaction (dev_list=, has_props=, props=, errp=errp@entry=0x7ffe4a1fc9d8) at blockdev.c:2308 Signed-off-by: Stefan Hajnoczi --- blockdev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/blockdev.c b/blockdev.c index 56a6b24a0b..3c8d994ced 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1812,8 +1812,8 @@ static void external_snapshot_clean(BlkActionState *common) DO_UPCAST(ExternalSnapshotState, common, common); if (state->aio_context) { bdrv_drained_end(state->old_bs); - aio_context_release(state->aio_context); bdrv_unref(state->new_bs); + aio_context_release(state->aio_context); } } -- 2.14.3