linux-kernel - Re: [PATCH 10/10] block: fix request_queue lifetime handling by making blk_queue

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20111019173337.GH25124@google.com>
Date:	Wed, 19 Oct 2011 10:33:37 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	axboe@...nel.dk, linux-kernel@...r.kernel.org, ctalbott@...gle.com
Subject: Re: [PATCH 10/10] block: fix request_queue lifetime handling by
 making blk_queue_cleanup() proper shutdown

Hello,

On Wed, Oct 19, 2011 at 01:29:14PM -0400, Vivek Goyal wrote:
> > Hmmm... the thing is you need to check DEAD again once after releasing
> > and re-grabbing the queuelock, os if we move the test into the caller,
> > we end up having one in the caller and one in the callee, so I thought
> > it would be better to keep them in the same function.
> 
> Sorry I did not get that why do we need to check again for DEAD after
> realeasing the queue lock. From throttling perspective, we grab lock
> once, if queue is DEAD, release lock and just return.
> 
> blk_throtl_bio() {
> 
>   bunch_of_checks_without_queue_lock;
> 
>   spin_lock()
>   if (queue_dead) {
> 	spin_unlock()
> 	return;
>   }
> 
>   throtl_get_tg();
> }	

Because DEAD state is protected by queue_lock and get_tg may release
and re-grab queue_lock across allocation?  It needs to re-test after
re-grabbing.

Thanks.

-- 
tejun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/