linux-kernel - Re: [patch]block: fix ioc locking warning

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: <4F303506.9000201@kernel.dk>
Date:	Mon, 06 Feb 2012 21:16:06 +0100
From:	Jens Axboe <axboe@...nel.dk>
To:	Tejun Heo <tj@...nel.org>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Vivek Goyal <vgoyal@...hat.com>,
	Shaohua Li <vivek.goyal2008@...il.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Knut Petersen <Knut_Petersen@...nline.de>, mroos@...ux.ee
Subject: Re: [patch]block: fix ioc locking warning

On 2012-02-06 18:27, Tejun Heo wrote:
> Hello,
> 
> On Mon, Feb 06, 2012 at 08:58:49AM -0800, Linus Torvalds wrote:
>> On Mon, Feb 6, 2012 at 8:44 AM, Tejun Heo <tj@...nel.org> wrote:
>>>
>>> Yeah, this seems better to me.  Jens, if you're gonna amend the
>>> commit, please consider collapsing the following patch into the
>>> original patch too.  Thanks.
>>
>> Guys, is it *really* worth it to do all these crazy games?
>>
>> How bad is it to just always use the async freeing, instead of this
>> clearly very fragile crazy direct-freeing-with-serious-locking-issues
>> thing?
> 
> It's one wq scheduling on exit for any task which has issued an IO.  I
> don't think it would matter except for task fork/exit microbenchs (or
> workloads which approximate to that).  I'll get some measurements and
> strip the optimization if it doesn't really show up.

One (arguably stupid) thing that some users do do is something like:

$ find . -exec grep foo '{}' \;

So that would probably be a good pathological test case for this.

-- 
Jens Axboe

--
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/