From: Paolo Bonzini <pbonzini@redhat.com>
To: "Denis V. Lunev" <den@openvz.org>
Cc: Amit Shah <amit.shah@redhat.com>,
qemu-stable@nongnu.org, qemu-devel@nongnu.org,
Stefan Hajnoczi <stefanha@redhat.com>,
Juan Quintela <quintela@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 4/5] migration: add missed aio_context_acquire into hmp_savevm/hmp_delvm
Date: Tue, 27 Oct 2015 19:12:31 +0100 [thread overview]
Message-ID: <562FBE8F.7040309@redhat.com> (raw)
In-Reply-To: <1445954986-13005-5-git-send-email-den@openvz.org>
On 27/10/2015 15:09, Denis V. Lunev wrote:
> aio_context should be locked in the similar way as was done in QMP
> snapshot creation in the other case there are a lot of possible
> troubles if native AIO mode is enabled for disk.
>
> - the command can hang (HMP thread) with missed wakeup (the operation is
> actually complete)
> io_submit
> ioq_submit
> laio_submit
> raw_aio_submit
> raw_aio_readv
> bdrv_co_io_em
> bdrv_co_readv_em
> bdrv_aligned_preadv
> bdrv_co_do_preadv
> bdrv_co_do_readv
> bdrv_co_readv
> qcow2_co_readv
> bdrv_aligned_preadv
> bdrv_co_do_pwritev
> bdrv_rw_co_entry
>
> - QEMU can assert in coroutine re-enter
> __GI_abort
> qemu_coroutine_enter
> bdrv_co_io_em_complete
> qemu_laio_process_completion
> qemu_laio_completion_bh
> aio_bh_poll
> aio_dispatch
> aio_poll
> iothread_run
>
> AioContext lock is reqursive. Thus nested locking should not be a problem.
>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Juan Quintela <quintela@redhat.com>
> CC: Amit Shah <amit.shah@redhat.com>
> ---
> block/snapshot.c | 5 +++++
> migration/savevm.c | 7 +++++++
> 2 files changed, 12 insertions(+)
>
> diff --git a/block/snapshot.c b/block/snapshot.c
> index 89500f2..f6fa17a 100644
> --- a/block/snapshot.c
> +++ b/block/snapshot.c
> @@ -259,6 +259,9 @@ void bdrv_snapshot_delete_by_id_or_name(BlockDriverState *bs,
> {
> int ret;
> Error *local_err = NULL;
> + AioContext *aio_context = bdrv_get_aio_context(bs);
> +
> + aio_context_acquire(aio_context);
>
> ret = bdrv_snapshot_delete(bs, id_or_name, NULL, &local_err);
> if (ret == -ENOENT || ret == -EINVAL) {
> @@ -267,6 +270,8 @@ void bdrv_snapshot_delete_by_id_or_name(BlockDriverState *bs,
> ret = bdrv_snapshot_delete(bs, NULL, id_or_name, &local_err);
> }
>
> + aio_context_release(aio_context);
Why here and not in hmp_delvm, for consistency?
The call from hmp_savevm is already protected.
Thanks for fixing the bug!
Paolo
> if (ret < 0) {
> error_propagate(errp, local_err);
> }
> diff --git a/migration/savevm.c b/migration/savevm.c
> index dbcc39a..83d2efa 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -1289,6 +1289,7 @@ void hmp_savevm(Monitor *mon, const QDict *qdict)
> struct tm tm;
> const char *name = qdict_get_try_str(qdict, "name");
> Error *local_err = NULL;
> + AioContext *aio_context;
>
> /* Verify if there is a device that doesn't support snapshots and is writable */
> bs = NULL;
> @@ -1320,6 +1321,9 @@ void hmp_savevm(Monitor *mon, const QDict *qdict)
> }
> vm_stop(RUN_STATE_SAVE_VM);
>
> + aio_context = bdrv_get_aio_context(bs);
> + aio_context_acquire(aio_context);
> +
> memset(sn, 0, sizeof(*sn));
>
> /* fill auxiliary fields */
> @@ -1378,6 +1382,8 @@ void hmp_savevm(Monitor *mon, const QDict *qdict)
> }
>
> the_end:
> + aio_context_release(aio_context);
> +
> if (saved_vm_running) {
> vm_start();
> }
>
>
next prev parent reply other threads:[~2015-10-27 18:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-27 14:09 [Qemu-devel] [PATCH v2 0/5] dataplane snapshot fixes Denis V. Lunev
2015-10-27 14:09 ` [Qemu-devel] [PATCH 1/5] fifolock: create rfifolock_is_locked helper Denis V. Lunev
2015-10-27 14:09 ` [Qemu-devel] [PATCH 2/5] aio_context: create aio_context_is_locked helper Denis V. Lunev
2015-10-27 14:09 ` [Qemu-devel] [PATCH 3/5] io: add locking constraints check into bdrv_drain to ensure locking Denis V. Lunev
2015-10-27 14:09 ` [Qemu-devel] [PATCH 4/5] migration: add missed aio_context_acquire into hmp_savevm/hmp_delvm Denis V. Lunev
2015-10-27 18:12 ` Paolo Bonzini [this message]
2015-10-27 18:23 ` Denis V. Lunev
2015-10-28 10:11 ` Juan Quintela
2015-10-28 10:38 ` Denis V. Lunev
2015-10-27 14:09 ` [Qemu-devel] [PATCH 5/5] virtio: sync the dataplane vring state to the virtqueue before virtio_save Denis V. Lunev
2015-10-27 18:41 ` [Qemu-devel] [PATCH v2 0/5] dataplane snapshot fixes Paolo Bonzini
2015-10-27 19:05 ` Denis V. Lunev
2015-10-27 23:22 ` Denis V. Lunev
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=562FBE8F.7040309@redhat.com \
--to=pbonzini@redhat.com \
--cc=amit.shah@redhat.com \
--cc=den@openvz.org \
--cc=qemu-devel@nongnu.org \
--cc=qemu-stable@nongnu.org \
--cc=quintela@redhat.com \
--cc=stefanha@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).