linux-kernel - Re: [PATCH 00/21] workqueue: cleanups and better locking for recent changes

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: <20130320183037.GE30484@htj.dyndns.org>
Date:	Wed, 20 Mar 2013 11:30:37 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/21] workqueue: cleanups and better locking for recent
 changes

So, overall,

On Wed, Mar 20, 2013 at 03:28:00AM +0800, Lai Jiangshan wrote:
...
> In this list, we can find that:
> 1) wq_mutex protects too much different kind of things.

I don't agree with this and unless you can come up with a much better
reason, won't be splitting wq_mutex further.  Also, I'm not gonna
rename it to wqs_mutex.

> 2) workqueue->pwqs are protected by both wq->flush_mutex and pwq_lock,
>    but in many read sites, they are protected by both wq->flush_mutex and pwq_lock,
>    in some other read sites, they are protected by pwq_lock, but can be converted
>    to wq->flush_mutex. it means pwq_lock and wq->flush_mutex are redundancy here.
> 3) pwq_lock is global lock, but it protects only workqueue instance fields.

A global lock protecting different instances is perfectly fine unless
it actually causes contention in some paths.  It often actually is
better to have a single global lock for cold paths as it pollutes less
amount of cache, so please don't split locks for that reason.

That said, I like the fact that wq->flush_mutex can be transformed
into wq->mutex and replaces pwq_lock making it go away, so, yeah, for
that reason, I like pwq_lock removal, so yeah, let's replace pwq_lock
with wq->mutex.

I applied the ones I can apply at this point.  I'll rebase the NUMA
patchset on top of the applied ones.  Please update the rest on top.

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/