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From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <fam@euphon.net>,
	Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
	qemu-block@nongnu.org, qemu-devel@nongnu.org,
	Hanna Reitz <hreitz@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>, John Snow <jsnow@redhat.com>
Subject: Re: [RFC PATCH v2 0/8] Removal of AioContext lock, bs->parents and ->children: new rwlock
Date: Fri, 29 Apr 2022 10:06:28 +0200	[thread overview]
Message-ID: <876f8360-bd93-8dc9-2e4a-d35f545152f6@redhat.com> (raw)
In-Reply-To: <Ymptphd9lpctkTj/@stefanha-x1.localdomain>



Am 28/04/2022 um 12:34 schrieb Stefan Hajnoczi:
> On Tue, Apr 26, 2022 at 04:51:06AM -0400, Emanuele Giuseppe Esposito wrote:
>> Next step is the most complex one: figure where to put the rdlocks.
> 
> I got a little lost at this step but will hopefully understand more when
> reading the patches. Earlier it said there is a counter for readers, so
> it seems trivial to make it a recursive lock. I don't understand why you
> want to avoid a recursive locking - the complications you described stem
> from the fact that you want to avoid recursive locks?

I'll let Paolo to further elaborate on this. I think it would be cleaner
if we try at least not to have recursive locks.

> 
> Secondly, can you describe the role of the lock? The text mentions the
> old AioContext lock that is being replaced but doesn't define this new
> lock in its own right. Is the idea to make ->parents and ->children list
> accesses thread-safe and all loops "safe" so they don't break when a BDS
> is removed?

Yes. Replace what AioContext lock is doing right now.

Emanuele
> 
> Stefan
> 



  reply	other threads:[~2022-04-29  8:12 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 [this message]
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
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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