From 96ba2c5dcbe1bed81311a8a150712a3bb25b9296 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Fri, 22 Dec 2017 11:08:49 +0100 Subject: [PATCH 31/42] blockdev: hold AioContext for bdrv_unref() in external_snapshot_clean() RH-Author: Stefan Hajnoczi Message-id: <20171222110900.24813-10-stefanha@redhat.com> Patchwork-id: 78490 O-Subject: [RHV7.5 qemu-kvm-rhev PATCH 09/20] blockdev: hold AioContext for bdrv_unref() in external_snapshot_clean() Bugzilla: 1519721 RH-Acked-by: Paolo Bonzini RH-Acked-by: Jeffrey Cody RH-Acked-by: Miroslav Rezanina 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 Reviewed-by: Kevin Wolf Reviewed-by: Eric Blake Message-id: 20171206144550.22295-2-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi (cherry picked from commit b9464ba19f821ea6b29969104dc48dcdb26243dd) Signed-off-by: Stefan Hajnoczi Signed-off-by: Miroslav Rezanina --- blockdev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/blockdev.c b/blockdev.c index 6a37934..c6978a5 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1855,8 +1855,8 @@ 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); } } -- 1.8.3.1