linux-kernel - Re: [PATCH] fix-flush_workqueue-vs-cpu

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: <20070106173416.GA3771@tv-sign.ru>
Date:	Sat, 6 Jan 2007 20:34:16 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Srivatsa Vaddagiri <vatsa@...ibm.com>
Cc:	Andrew Morton <akpm@...l.org>, David Howells <dhowells@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...l.org>,
	linux-kernel@...r.kernel.org, Gautham shenoy <ego@...ibm.com>
Subject: Re: [PATCH] fix-flush_workqueue-vs-cpu_dead-race-update

On 01/06, Srivatsa Vaddagiri wrote:
>
> On Sat, Jan 06, 2007 at 07:30:35PM +0300, Oleg Nesterov wrote:
> > Stupid me. Thanks.
> > 
> > I'll try to do something else tomorrow. Do you see a simple soulution?
> 
> Sigh ..I dont see a simple solution, unless we have something like
> lock_cpu_hotplug() ..

I suspect this can't help either.

The problem is that flush_workqueue() may be called while cpu hotplug event
in progress and CPU_DEAD waits for kthread_stop(), so we have the same dead
lock if work->func() does flush_workqueue(). This means that Andrew's change
to use preempt_disable() is good and anyway needed.

I am starting to believe we need some more intrusive changes in workquue.c.

Oleg.

-
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/