Re: [2.6.33-rc5] Weird deadlock when shutting down

[Johannes Berg]

On Sun, 2010-02-21 at 19:12 +0800, Xiaotian Feng wrote:
> On Sun, Feb 21, 2010 at 6:55 PM, Xiaotian Feng <xtfeng@xxxxxxxxx>
> wrote:
> > On Sun, Feb 21, 2010 at 6:43 PM, Johannes Berg
> > <johannes@xxxxxxxxxxxxxxxx> wrote:
> >> Incidentally, the machine also freezes hard without any output at
> all if
> >> I "echo 0 > /sys/.../cpu1/online".
> >
> > It might be nothing related with cpufreq. I think there's something
> > wrong during the _cpu_down path.
> > put more debug printks into _cpu_down(), if we can find kernel is
> > stuck in which place in _cpu_down, it would be helpful.
> 
> and it looks like this breakage is only seen on powerMac G5, so it
> might be arch specific. Maybe some commit in powermac breaks G5's
> cpu_down, just a guess ;-)

Hmm, not sure ... it seems to be in __stop_machine(), in this code:

        printk("got cpu\n");
        for_each_online_cpu(i) {
                sm_work = per_cpu_ptr(stop_machine_work, i);
                INIT_WORK(sm_work, stop_cpu);
                queue_work_on(i, stop_machine_wq, sm_work);
        }
        /* This will release the thread on our CPU. */
        put_cpu();
        printk("put cpu\n");


which is weird... the "got cpu" printk is the last thing I see.

johannes

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