From: Stefan Reiter <s.reiter@proxmox.com>
To: qemu-devel@nongnu.org, qemu-block@nongnu.org
Cc: kwolf@redhat.com, vsementsov@virtuozzo.com, mreitz@redhat.com,
stefanha@redhat.com, jsnow@redhat.com, dietmar@proxmox.com
Subject: [PATCH] backup: don't acquire aio_context in backup_clean
Date: Wed, 25 Mar 2020 16:50:55 +0100 [thread overview]
Message-ID: <20200325155055.730633-1-s.reiter@proxmox.com> (raw)
In-Reply-To: <76edbead-7ccf-833b-a3f2-15dff7f0748c@virtuozzo.com>
backup_clean is only ever called as a handler via job_exit, which
already acquires the job's context. The job's context is guaranteed to
be the same as the one used by backup_top via backup_job_create.
Since the previous logic effectively acquired the lock twice, this
broke cleanup of backups for disks using IO threads, since the BDRV_POLL_WHILE
in bdrv_backup_top_drop -> bdrv_do_drained_begin would only release the lock
once, thus deadlocking with the IO thread.
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
---
This is a fix for the issue discussed in this part of the thread:
https://lists.gnu.org/archive/html/qemu-devel/2020-03/msg07639.html
...not the original problem (core dump) posted by Dietmar.
I've still seen it occasionally hang during a backup abort. I'm trying to figure
out why that happens, stack trace indicates a similar problem with the main
thread hanging at bdrv_do_drained_begin, though I have no clue why as of yet.
block/backup.c | 4 ----
1 file changed, 4 deletions(-)
diff --git a/block/backup.c b/block/backup.c
index 7430ca5883..a7a7dcaf4c 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -126,11 +126,7 @@ static void backup_abort(Job *job)
static void backup_clean(Job *job)
{
BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
- AioContext *aio_context = bdrv_get_aio_context(s->backup_top);
-
- aio_context_acquire(aio_context);
bdrv_backup_top_drop(s->backup_top);
- aio_context_release(aio_context);
}
void backup_do_checkpoint(BlockJob *job, Error **errp)
--
2.25.2
next prev parent reply other threads:[~2020-03-25 15:51 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-24 11:13 backup transaction with io-thread core dumps Dietmar Maurer
2020-03-24 13:30 ` Dietmar Maurer
2020-03-24 13:33 ` Dietmar Maurer
2020-03-24 13:44 ` John Snow
2020-03-24 14:00 ` Dietmar Maurer
2020-03-24 13:47 ` Max Reitz
2020-03-24 14:02 ` Dietmar Maurer
2020-03-24 16:49 ` Dietmar Maurer
2020-03-25 11:40 ` Stefan Reiter
2020-03-25 12:23 ` Vladimir Sementsov-Ogievskiy
2020-03-25 15:50 ` Stefan Reiter [this message]
2020-03-26 5:54 ` [PATCH] backup: don't acquire aio_context in backup_clean Vladimir Sementsov-Ogievskiy
2020-03-26 9:43 ` Stefan Reiter
2020-03-26 12:46 ` Vladimir Sementsov-Ogievskiy
2020-03-26 11:53 ` Sergio Lopez
2020-03-25 8:13 ` backup transaction with io-thread core dumps Sergio Lopez
2020-03-25 11:46 ` Sergio Lopez
2020-03-25 12:29 ` Dietmar Maurer
2020-03-25 12:39 ` Sergio Lopez
2020-03-25 15:40 ` Dietmar Maurer
2020-03-26 7:50 ` Sergio Lopez
2020-03-26 8:14 ` Dietmar Maurer
2020-03-26 9:23 ` Dietmar Maurer
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