From: Oleg Nesterov <oleg@redhat.com>
To: Petr Mladek <pmladek@suse.com>
Cc: akpm@linux-foundation.org, bp@suse.de, davidchao@google.com,
jenhaochen@google.com, jkosina@suse.cz, josh@joshtriplett.org,
liumartin@google.com, mhocko@suse.cz, mingo@redhat.com,
mm-commits@vger.kernel.org, nathan@kernel.org,
ndesaulniers@google.com, paulmck@linux.vnet.ibm.com,
peterz@infradead.org, rostedt@goodmis.org,
stable@vger.kernel.org, tglx@linutronix.de, tj@kernel.org,
vbabka@suse.cz, linux-kernel@vger.kernel.org
Subject: Re: + kthread-fix-kthread_mod_delayed_work-vs-kthread_cancel_delayed_work_sync-race.patch added to -mm tree
Date: Wed, 26 May 2021 19:06:06 +0200 [thread overview]
Message-ID: <20210526170604.GC4581@redhat.com> (raw)
In-Reply-To: <YKvBVIJAc8/Qasdu@alley>
On 05/24, Petr Mladek wrote:
>
> Your patch changes the semantic. The current semantic is the same for
> the workqueue's counter-part mod_delayed_work_on().
OK, I see, thanks. I was confused by the comment.
> We should actually keep the "ret" value as is to stay compatible with
> workqueue API:
>
> /*
> * Canceling could run in parallel from kthread_cancel_delayed_work_sync
> * and change work's canceling count as the spinlock is released and regain
> * in __kthread_cancel_work so we need to check the count again. Otherwise,
> * we might incorrectly queue the dwork and further cause
> * cancel_delayed_work_sync thread waiting for flush dwork endlessly.
> *
> * Keep the ret code. The API primary informs the caller
> * whether some pending work has been canceled (not proceed).
> */
> if (work->canceling)
> goto out;
Agreed, we should keep the "ret" value.
but unless I am confused again this doesn't match mod_delayed_work_on()
which always returns true if it races with cancel(). Nevermind, I think
this doesn't matter.
Thanks,
Oleg.
next prev parent reply other threads:[~2021-05-26 17:06 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210520214737.MrGGKbPrJ%akpm@linux-foundation.org>
2021-05-21 16:35 ` + kthread-fix-kthread_mod_delayed_work-vs-kthread_cancel_delayed_work_sync-race.patch added to -mm tree Oleg Nesterov
2021-05-24 15:08 ` Petr Mladek
2021-05-26 17:06 ` Oleg Nesterov [this message]
2021-05-27 10:15 ` Petr Mladek
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