From: Andrew Morton <akpm@linux-foundation.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Mike Travis <travis@sgi.com>, Ingo Molnar <mingo@redhat.com>,
Dave Jones <davej@redhat.com>,
cpufreq@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] work_on_cpu: Use our own workqueue.
Date: Wed, 28 Jan 2009 18:12:05 -0800 [thread overview]
Message-ID: <20090128181205.3b15fa4a.akpm@linux-foundation.org> (raw)
In-Reply-To: <200901291213.32959.rusty@rustcorp.com.au>
On Thu, 29 Jan 2009 12:13:32 +1030 Rusty Russell <rusty@rustcorp.com.au> wrote:
> On Thursday 29 January 2009 06:14:40 Andrew Morton wrote:
> > It's vulnerable to the same deadlock, I think? Suppose we have:
> ...
> > - A calls work_on_cpu() and takes woc_mutex.
> >
> > - Before function_which_takes_L() has started to execute, task B takes L
> > then calls work_on_cpu() and task B blocks on woc_mutex.
> >
> > - Now function_which_takes_L() runs, and blocks on L
>
> Agreed, but now it's a fairly simple case. Both sides have to take lock L, and both have to call work_on_cpu.
>
> Workqueues are more generic and widespread, and an amazing amount of stuff gets called from them. That's why I felt uncomfortable with removing the one known problematic caller.
>
hm. it's a bit of a timebomb.
y'know, the original way in which acpi-cpufreq did this is starting to
look attractive. Migrate self to that CPU then just call the dang
function. Slow, but no deadlocks (I think)?
next prev parent reply other threads:[~2009-01-29 2:12 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-16 19:11 [PATCH 0/3] cpu freq: fix problems with work_on_cpu usage in acpi-cpufreq Mike Travis
2009-01-16 19:11 ` [PATCH 1/3] work_on_cpu: dont try to get_online_cpus() in work_on_cpu Mike Travis
2009-01-16 19:11 ` [PATCH 2/3] work_on_cpu: Use our own workqueue Mike Travis
2009-01-24 8:15 ` Andrew Morton
[not found] ` <200901261711.43943.rusty@rustcorp.com.au>
2009-01-26 7:01 ` Andrew Morton
2009-01-26 17:16 ` Ingo Molnar
2009-01-26 18:35 ` Andrew Morton
2009-01-26 20:20 ` Ingo Molnar
2009-01-26 20:43 ` Mike Travis
2009-01-26 21:00 ` Andrew Morton
2009-01-26 21:27 ` Ingo Molnar
2009-01-26 21:35 ` Andrew Morton
2009-01-26 21:45 ` Ingo Molnar
2009-01-26 22:01 ` Andrew Morton
2009-01-26 22:05 ` Ingo Molnar
2009-01-26 22:16 ` Andrew Morton
2009-01-26 22:20 ` Ingo Molnar
2009-01-26 22:50 ` Andrew Morton
2009-01-26 22:59 ` Ingo Molnar
2009-01-26 23:42 ` Andrew Morton
2009-01-26 23:53 ` Ingo Molnar
2009-01-27 0:42 ` Andrew Morton
2009-01-26 22:31 ` Oleg Nesterov
2009-01-26 22:15 ` Oleg Nesterov
2009-01-26 22:24 ` Ingo Molnar
2009-01-26 22:37 ` Oleg Nesterov
2009-01-26 22:42 ` Ingo Molnar
2009-01-26 21:50 ` Oleg Nesterov
2009-01-26 22:17 ` Ingo Molnar
2009-01-26 23:01 ` Mike Travis
2009-01-27 0:09 ` Oleg Nesterov
2009-01-27 7:15 ` Rusty Russell
2009-01-27 17:55 ` Oleg Nesterov
2009-01-27 7:05 ` Rusty Russell
2009-01-27 7:25 ` Andrew Morton
2009-01-27 15:28 ` Ingo Molnar
2009-01-27 16:51 ` Andrew Morton
2009-01-28 13:02 ` Rusty Russell
2009-01-28 17:19 ` Mike Travis
2009-01-28 17:32 ` Mike Travis
2009-01-29 10:39 ` Rusty Russell
2009-01-28 19:44 ` Andrew Morton
2009-01-29 1:43 ` Rusty Russell
2009-01-29 2:12 ` Andrew Morton [this message]
2009-01-30 6:03 ` Rusty Russell
2009-01-30 6:30 ` Andrew Morton
2009-01-30 13:49 ` Ingo Molnar
2009-01-30 17:08 ` Andrew Morton
2009-01-30 21:59 ` Rusty Russell
2009-01-30 22:17 ` Andrew Morton
2009-02-02 12:35 ` Rusty Russell
2009-02-03 4:06 ` Andrew Morton
2009-02-04 2:44 ` Rusty Russell
2009-02-04 3:01 ` Andrew Morton
2009-02-04 10:41 ` Rusty Russell
2009-02-04 15:36 ` Andrew Morton
2009-02-04 21:35 ` Ingo Molnar
2009-02-04 21:48 ` Andrew Morton
2009-02-04 21:54 ` Ingo Molnar
2009-02-04 23:45 ` Rusty Russell
2009-02-05 12:19 ` Pavel Machek
2009-02-05 17:44 ` Dmitry Adamushko
2009-02-10 8:54 ` Rusty Russell
2009-02-10 9:35 ` Andrew Morton
2009-02-11 0:32 ` Rusty Russell
2009-01-16 19:11 ` [PATCH 3/3] cpufreq: use work_on_cpu in acpi-cpufreq.c for drv_read and drv_write Mike Travis
2009-01-16 23:38 ` [PATCH 0/3] cpu freq: fix problems with work_on_cpu usage in acpi-cpufreq [PULL request] Mike Travis
2009-01-17 22:08 ` Ingo Molnar
2009-01-19 17:11 ` Mike Travis
2009-01-19 17:26 ` Ingo Molnar
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