From: Ingo Molnar <mingo@elte.hu>
To: Andrew Morton <akpm@osdl.org>
Cc: vatsa@in.ibm.com, Bjorn Helgaas <bjorn.helgaas@hp.com>,
linux-kernel@vger.kernel.org, Myron Stowe <myron.stowe@hp.com>,
Jens Axboe <axboe@kernel.dk>, Dipankar <dipankar@in.ibm.com>,
Gautham shenoy <ego@in.ibm.com>
Subject: Re: workqueue deadlock
Date: Sun, 10 Dec 2006 13:19:15 +0100 [thread overview]
Message-ID: <20061210121914.GA20466@elte.hu> (raw)
In-Reply-To: <20061210041600.56306676.akpm@osdl.org>
* Andrew Morton <akpm@osdl.org> wrote:
> This is actually not cpu-hotplug safe ;)
>
> > > > {
> > > > int cpu = raw_smp_processor_id();
> > > > /*
> > > > * Interrupts/softirqs are hotplug-safe:
> > > > */
> > > > if (in_interrupt())
> > > > return;
> > > > if (current->hotplug_depth++)
> > > > return;
>
> <preempt, cpu hot-unplug, resume on different CPU>
>
> > > > current->hotplug_lock = &per_cpu(hotplug_lock, cpu);
>
> <use-after-free>
>
> > > > mutex_lock(current->hotplug_lock);
>
> And it sleeps, so we can't use preempt_disable().
i explained it in the other mail - this is the 'read' side. The 'write'
side (code actually wanting to /do/ a CPU hotplug state transition) has
to take /all/ these locks before it can take a CPU down.
so this is still a global CPU hotplug lock, but made scalable.
Ingo
next prev parent reply other threads:[~2006-12-10 12:21 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-07 0:26 workqueue deadlock Bjorn Helgaas
2006-12-07 6:17 ` Srivatsa Vaddagiri
2006-12-07 6:45 ` Srivatsa Vaddagiri
2006-12-07 18:51 ` Andrew Morton
2006-12-07 19:37 ` Andrew Morton
2006-12-08 2:53 ` Srivatsa Vaddagiri
2006-12-08 4:54 ` Andrew Morton
2006-12-08 7:58 ` Srivatsa Vaddagiri
2006-12-09 10:26 ` Ingo Molnar
2006-12-09 19:47 ` Andrew Morton
2006-12-10 8:26 ` Ingo Molnar
2006-12-10 8:43 ` Andrew Morton
2006-12-10 11:49 ` Ingo Molnar
2006-12-10 12:16 ` Andrew Morton
2006-12-10 12:19 ` Ingo Molnar [this message]
2006-12-10 12:34 ` Andrew Morton
2006-12-11 6:09 ` Ingo Molnar
2006-12-10 14:18 ` Rafael J. Wysocki
2006-12-11 6:52 ` Dipankar Sarma
2006-12-11 16:34 ` Rafael J. Wysocki
2006-12-11 5:45 ` Srivatsa Vaddagiri
2006-12-11 6:03 ` Andrew Morton
2006-12-11 4:58 ` Srivatsa Vaddagiri
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