DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com E302F7ACA2
Subject: Re: [PATCH v2] blktrace: Fix potentail deadlock between delete &
 sysfs ops
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Jens Axboe <axboe@kernel.dk>, Jeff Layton <jlayton@poochiereds.net>,
        "J. Bruce Fields" <bfields@fieldses.org>,
        Ingo Molnar <mingo@kernel.org>, linux-kernel@vger.kernel.org,
        linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org
References: <1502916040-18067-1-git-send-email-longman@redhat.com>
 <20170817093444.3276f7ab@gandalf.local.home>
 <b0719c60-5c07-d121-1c84-d5993d36afb0@redhat.com>
 <20170817171007.1ab33b8f@gandalf.local.home>
 <20170817173004.263d2891@gandalf.local.home>
From: Waiman Long <longman@redhat.com>
Organization: Red Hat
Message-ID: <5a5d0743-d2db-89c8-59cc-542835baeccf@redhat.com>
Date: Fri, 18 Aug 2017 09:55:58 -0400
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.2.0
MIME-Version: 1.0
In-Reply-To: <20170817173004.263d2891@gandalf.local.home>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8BIT
Content-Language: en-US
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 821
Lines: 23

On 08/17/2017 05:30 PM, Steven Rostedt wrote:
> On Thu, 17 Aug 2017 17:10:07 -0400
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
>
>> Instead of playing games with taking the lock, the only way this race
>> is hit, is if the partition is being deleted and the sysfs attribute is
>> being read at the same time, correct? In that case, just return
>> -ENODEV, and be done with it.
> Nevermind that wont work. Too bad there's not a mutex_lock_timeout()
> that we could use in a loop. It would solve the issue of forward
> progress with RT tasks, and will break after a timeout in case of
> deadlock.
>
> -- Steve

I think it will be useful to have mutex_timed_lock(). RT-mutex does have
a timed version, so I guess it shouldn't be hard to implement one for
mutex. I can take a shot at trying to do that.

Thanks,
Longman