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From: Stefan Hajnoczi <stefanha@redhat.com>
To: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Cc: qemu-block@nongnu.org, Kevin Wolf <kwolf@redhat.com>,
	Hanna Reitz <hreitz@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>, John Snow <jsnow@redhat.com>,
	Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
	Wen Congyang <wencongyang2@huawei.com>,
	Xie Changlong <xiechanglong.d@gmail.com>,
	Markus Armbruster <armbru@redhat.com>, Fam Zheng <fam@euphon.net>,
	qemu-devel@nongnu.org
Subject: Re: [PATCH v8 17/20] job.c: enable job lock/unlock and remove Aiocontext locks
Date: Tue, 5 Jul 2022 14:07:59 +0100	[thread overview]
Message-ID: <YsQ3r398HXi9B92H@stefanha-x1.localdomain> (raw)
In-Reply-To: <20220629141538.3400679-18-eesposit@redhat.com>

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On Wed, Jun 29, 2022 at 10:15:35AM -0400, Emanuele Giuseppe Esposito wrote:
> Change the job_{lock/unlock} and macros to use job_mutex.
> 
> Now that they are not nop anymore, remove the aiocontext
> to avoid deadlocks.
> 
> Therefore:
> - when possible, remove completely the aiocontext lock/unlock pair
> - if it is used by some other function too, reduce the locking
> section as much as possible, leaving the job API outside.
> 
> There is only one JobDriver callback, ->free() that assumes that
> the aiocontext lock is held (because it calls bdrv_unref), so for
> now keep that under aiocontext lock.

This discussion shouldn't hold up the patch series, it's a separate
issue:

Why does bdrv_unref() need the AioContext lock? The reference count
itself is protected by the BQL (bdrv_ref() is GS too). I/O requests
should be using fine-grained locks now, so I'm not sure if we still need
to hold the AioContext lock to drain them?

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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  reply	other threads:[~2022-07-05 13:10 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-29 14:15 [PATCH v8 00/20] job: replace AioContext lock with job_mutex Emanuele Giuseppe Esposito
2022-06-29 14:15 ` [PATCH v8 01/20] job.c: make job_mutex and job_lock/unlock() public Emanuele Giuseppe Esposito
2022-06-29 14:15 ` [PATCH v8 02/20] job.h: categorize fields in struct Job Emanuele Giuseppe Esposito
2022-07-05  7:29   ` Stefan Hajnoczi
2022-06-29 14:15 ` [PATCH v8 03/20] job.c: API functions not used outside should be static Emanuele Giuseppe Esposito
2022-06-29 14:15 ` [PATCH v8 04/20] aio-wait.h: introduce AIO_WAIT_WHILE_UNLOCKED Emanuele Giuseppe Esposito
2022-06-29 14:15 ` [PATCH v8 05/20] job.c: add job_lock/unlock while keeping job.h intact Emanuele Giuseppe Esposito
2022-07-05  7:39   ` Stefan Hajnoczi
2022-07-05  8:07     ` Emanuele Giuseppe Esposito
2022-07-06 10:09       ` Stefan Hajnoczi
2022-07-05  7:39   ` Stefan Hajnoczi
2022-07-05 10:23   ` Vladimir Sementsov-Ogievskiy
2022-06-29 14:15 ` [PATCH v8 06/20] job.h: define functions called without job lock held Emanuele Giuseppe Esposito
2022-07-05  7:43   ` Stefan Hajnoczi
2022-07-05 10:53   ` Vladimir Sementsov-Ogievskiy
2022-07-06  8:22     ` Emanuele Giuseppe Esposito
2022-07-06  9:48       ` Vladimir Sementsov-Ogievskiy
2022-07-05 10:54   ` Vladimir Sementsov-Ogievskiy
2022-07-06  8:23     ` Emanuele Giuseppe Esposito
2022-07-06  9:51       ` Vladimir Sementsov-Ogievskiy
2022-06-29 14:15 ` [PATCH v8 07/20] job.h: add _locked public functions Emanuele Giuseppe Esposito
2022-07-05  7:44   ` Stefan Hajnoczi
2022-07-05 10:58   ` Vladimir Sementsov-Ogievskiy
2022-06-29 14:15 ` [PATCH v8 08/20] blockjob.h: introduce block_job _locked() APIs Emanuele Giuseppe Esposito
2022-07-05  7:58   ` Stefan Hajnoczi
2022-07-05  8:12     ` Emanuele Giuseppe Esposito
2022-07-05 15:01   ` Vladimir Sementsov-Ogievskiy
2022-07-06 12:05     ` Emanuele Giuseppe Esposito
2022-07-06 12:23       ` Vladimir Sementsov-Ogievskiy
2022-07-06 12:36         ` Emanuele Giuseppe Esposito
2022-07-06 12:59           ` Emanuele Giuseppe Esposito
2022-07-06 17:23             ` Vladimir Sementsov-Ogievskiy
2022-06-29 14:15 ` [PATCH v8 09/20] blockjob: rename notifier callbacks as _locked Emanuele Giuseppe Esposito
2022-07-05  8:00   ` Stefan Hajnoczi
2022-06-29 14:15 ` [PATCH v8 10/20] jobs: add job lock in find_* functions Emanuele Giuseppe Esposito
2022-07-05  8:03   ` Stefan Hajnoczi
2022-06-29 14:15 ` [PATCH v8 11/20] jobs: use job locks also in the unit tests Emanuele Giuseppe Esposito
2022-07-05  8:04   ` Stefan Hajnoczi
2022-06-29 14:15 ` [PATCH v8 12/20] block/mirror.c: use of job helpers in drivers to avoid TOC/TOU Emanuele Giuseppe Esposito
2022-06-29 14:15 ` [PATCH v8 13/20] jobs: group together API calls under the same job lock Emanuele Giuseppe Esposito
2022-07-05  8:14   ` Stefan Hajnoczi
2022-07-05  8:17     ` Emanuele Giuseppe Esposito
2022-07-05 13:01       ` Emanuele Giuseppe Esposito
2022-07-05 13:22         ` Vladimir Sementsov-Ogievskiy
2022-07-06 10:13           ` Stefan Hajnoczi
2022-07-05 14:55   ` Vladimir Sementsov-Ogievskiy
2022-06-29 14:15 ` [PATCH v8 14/20] commit and mirror: create new nodes using bdrv_get_aio_context, and not the job aiocontext Emanuele Giuseppe Esposito
2022-06-29 14:15 ` [PATCH v8 15/20] job: detect change of aiocontext within job coroutine Emanuele Giuseppe Esposito
2022-06-29 14:15 ` [PATCH v8 16/20] jobs: protect job.aio_context with BQL and job_mutex Emanuele Giuseppe Esposito
2022-07-05 12:44   ` Stefan Hajnoczi
2022-06-29 14:15 ` [PATCH v8 17/20] job.c: enable job lock/unlock and remove Aiocontext locks Emanuele Giuseppe Esposito
2022-07-05 13:07   ` Stefan Hajnoczi [this message]
2022-07-06 21:29     ` Emanuele Giuseppe Esposito
2022-06-29 14:15 ` [PATCH v8 18/20] block_job_query: remove atomic read Emanuele Giuseppe Esposito
2022-06-29 14:15 ` [PATCH v8 19/20] blockjob: remove unused functions Emanuele Giuseppe Esposito
2022-07-05 13:10   ` Stefan Hajnoczi
2022-06-29 14:15 ` [PATCH v8 20/20] job: " Emanuele Giuseppe Esposito
2022-07-05 13:11   ` Stefan Hajnoczi
2022-07-05 13:12 ` [PATCH v8 00/20] job: replace AioContext lock with job_mutex Stefan Hajnoczi

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