From: Paolo Bonzini <pbonzini@redhat.com>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
Emanuele Giuseppe Esposito <eesposit@redhat.com>,
qemu-block@nongnu.org, Hanna Reitz <hreitz@redhat.com>,
John Snow <jsnow@redhat.com>,
Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
Fam Zheng <fam@euphon.net>,
qemu-devel@nongnu.org
Subject: Re: [RFC PATCH v2 0/8] Removal of AioContext lock, bs->parents and ->children: new rwlock
Date: Tue, 24 May 2022 19:25:19 +0200 [thread overview]
Message-ID: <f0552d30-2dc8-df5f-6de9-c59a2a2951c1@redhat.com> (raw)
In-Reply-To: <Yoyxf4XDxhl4pDhr@stefanha-x1.localdomain>
On 5/24/22 12:20, Stefan Hajnoczi wrote:
>> Maybe it's safe to run it without a lock because it runs after
>> virtio_set_status(vdev, 0) but I'd rather play it safe and protect s->rq
>> with a lock.
>
> What does the lock protect?
>
> A lock can prevent s->rq or req->vq corruption but it cannot prevent
> request leaks. This loop's job is to free all requests so there is no
> leak. If a lock is necessary then this code is already broken in a more
> fundamental way because it can leak.
Yes, you're right. This particular list is always accessed in the
iothread (if any) and blk_drain() is enough. virtio-blk should already
not need aio_context_{acquire,release}.
It's worth a comment, though!
Paolo
next prev parent reply other threads:[~2022-05-24 17:27 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-26 8:51 [RFC PATCH v2 0/8] Removal of AioContext lock, bs->parents and ->children: new rwlock Emanuele Giuseppe Esposito
2022-04-26 8:51 ` [RFC PATCH v2 1/8] aio_wait_kick: add missing memory barrier Emanuele Giuseppe Esposito
2022-04-28 11:09 ` Stefan Hajnoczi
2022-04-29 8:06 ` Emanuele Giuseppe Esposito
2022-04-30 5:21 ` Stefan Hajnoczi
2022-04-29 8:12 ` Paolo Bonzini
2022-04-26 8:51 ` [RFC PATCH v2 2/8] coroutine-lock: release lock when restarting all coroutines Emanuele Giuseppe Esposito
2022-04-26 14:59 ` Paolo Bonzini
2022-04-28 11:21 ` Stefan Hajnoczi
2022-04-28 22:14 ` Paolo Bonzini
2022-04-29 9:35 ` Emanuele Giuseppe Esposito
2022-04-26 8:51 ` [RFC PATCH v2 3/8] block: introduce a lock to protect graph operations Emanuele Giuseppe Esposito
2022-04-26 15:00 ` Paolo Bonzini
2022-04-28 13:45 ` Stefan Hajnoczi
2022-04-29 8:37 ` Emanuele Giuseppe Esposito
2022-04-30 5:48 ` Stefan Hajnoczi
2022-05-02 7:54 ` Emanuele Giuseppe Esposito
2022-05-03 10:50 ` Stefan Hajnoczi
2022-04-26 8:51 ` [RFC PATCH v2 4/8] async: register/unregister aiocontext in graph lock list Emanuele Giuseppe Esposito
2022-04-28 13:46 ` Stefan Hajnoczi
2022-04-28 22:19 ` Paolo Bonzini
2022-04-29 8:37 ` Emanuele Giuseppe Esposito
2022-04-26 8:51 ` [RFC PATCH v2 5/8] block.c: wrlock in bdrv_replace_child_noperm Emanuele Giuseppe Esposito
2022-04-26 15:07 ` Paolo Bonzini
2022-04-28 13:55 ` Stefan Hajnoczi
2022-04-29 8:41 ` Emanuele Giuseppe Esposito
2022-04-26 8:51 ` [RFC PATCH v2 6/8] block: assert that graph read and writes are performed correctly Emanuele Giuseppe Esposito
2022-04-28 14:43 ` Stefan Hajnoczi
2022-04-26 8:51 ` [RFC PATCH v2 7/8] graph-lock: implement WITH_GRAPH_RDLOCK_GUARD and GRAPH_RDLOCK_GUARD macros Emanuele Giuseppe Esposito
2022-04-28 15:00 ` Stefan Hajnoczi
2022-04-26 8:51 ` [RFC PATCH v2 8/8] mirror: protect drains in coroutine with rdlock Emanuele Giuseppe Esposito
2022-04-27 6:55 ` [RFC PATCH v2 0/8] Removal of AioContext lock, bs->parents and ->children: new rwlock Emanuele Giuseppe Esposito
2022-04-28 10:45 ` Stefan Hajnoczi
2022-04-28 21:56 ` Emanuele Giuseppe Esposito
2022-04-30 5:17 ` Stefan Hajnoczi
2022-05-02 8:02 ` Emanuele Giuseppe Esposito
2022-05-02 13:15 ` Paolo Bonzini
2022-05-03 8:24 ` Kevin Wolf
2022-05-03 11:04 ` Stefan Hajnoczi
2022-04-28 10:34 ` Stefan Hajnoczi
2022-04-29 8:06 ` Emanuele Giuseppe Esposito
2022-05-04 13:39 ` Stefan Hajnoczi
2022-05-17 10:59 ` Stefan Hajnoczi
2022-05-18 12:28 ` Emanuele Giuseppe Esposito
2022-05-18 12:43 ` Paolo Bonzini
2022-05-18 14:57 ` Stefan Hajnoczi
2022-05-18 16:14 ` Kevin Wolf
2022-05-19 11:27 ` Stefan Hajnoczi
2022-05-19 12:52 ` Kevin Wolf
2022-05-22 15:06 ` Stefan Hajnoczi
2022-05-23 8:48 ` Emanuele Giuseppe Esposito
2022-05-23 13:15 ` Stefan Hajnoczi
2022-05-23 13:54 ` Emanuele Giuseppe Esposito
2022-05-23 13:02 ` Kevin Wolf
2022-05-23 15:13 ` Stefan Hajnoczi
2022-05-23 16:04 ` Kevin Wolf
2022-05-23 16:45 ` Stefan Hajnoczi
2022-05-24 7:55 ` Paolo Bonzini
2022-05-24 8:08 ` Stefan Hajnoczi
2022-05-24 9:17 ` Paolo Bonzini
2022-05-24 10:20 ` Stefan Hajnoczi
2022-05-24 17:25 ` Paolo Bonzini [this message]
2022-05-24 10:36 ` Kevin Wolf
2022-05-25 7:41 ` Paolo Bonzini
2022-05-18 14:27 ` Stefan Hajnoczi
2022-05-24 12:10 ` Kevin Wolf
2022-05-25 8:27 ` Emanuele Giuseppe Esposito
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