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SubjectRe: [linux-pm] Re: 2.6.21-rc7-mm2 suspend bug. [kernel/kthread.c]
On Mon, Apr 30, 2007 at 12:39:46AM -0700, Andrew Morton wrote:
> On Sun, 29 Apr 2007 22:27:44 +0200 "Rafael J. Wysocki" <rjw@sisk.pl> wrote:
>
> > On Sunday, 29 April 2007 21:51, Dan Kruchinin wrote:
> > > Hi all.
> > >
> > > There is a problem on my macbook core duo with suspend.
> > > after suspending when i'm trying to 'wake up' my notebook, it seems
> > > that it works, but i don't see anything at my monitor. So i have to
> > > reboot it to continue my work.
> >
> > What exactly do you do to suspend?
> >
>
> This is due to _cpu_down() calling kthread_bind() in state TASK_RUNNING.

The state should be TASK_INTERRUPTIBLE. That's the state of the thread
'p' should be in when we do a kthread_bind(p) in _cpu_down().

Are you sure about the TASK_RUNNING part ?

>
> So I was sent the below, including worrisome changelog.
>

Ok, it should not be that worrisome!
By the time we would be doing kthread_stop(p) in _cpu_down(), 'p' would have
been moved over to some other online cpu, due to the migrate_dead_tasks()
called in CPU_DEAD handling of migration_call (kernel/sched.c).

So we are safe. Anyway, I apologise for causing any worry :-)

Thanks and Regards
gautham.
>
>
>
> From: Gautham R Shenoy <ego@in.ibm.com>
>
> We are anyway kthread_stop()ping other per-cpu kernel threads after
> move_task_off_dead_cpu(), so we can do it with the stop_machine_run thread
> as well.
>
> I just checked with Vatsa if there was any subtle reason why they
> had put in the kthread_bind() in cpu.c. Vatsa cannot seem to recollect
> any and I can't see any. So let us just remove the kthread_bind.
>
> Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
> Cc: Oleg Nesterov <oleg@tv-sign.ru>
> Cc: "Eric W. Biederman" <ebiederm@xmission.com>
> Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> kernel/cpu.c | 4 ----
> 1 files changed, 4 deletions(-)
>
> diff -puN kernel/cpu.c~remvoe-kthread_bind-call-from-_cpu_down kernel/cpu.c
> --- a/kernel/cpu.c~remvoe-kthread_bind-call-from-_cpu_down
> +++ a/kernel/cpu.c
> @@ -175,10 +175,6 @@ static int _cpu_down(unsigned int cpu)
> /* This actually kills the CPU. */
> __cpu_die(cpu);
>
> - /* Move it here so it can run. */
> - kthread_bind(p, get_cpu());
> - put_cpu();
> -
> /* CPU is completely dead: tell everyone. Too late to complain. */
> if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD, hcpu) == NOTIFY_BAD)
> BUG();
> _
>
> _______________________________________________
> linux-pm mailing list
> linux-pm@lists.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/linux-pm

--
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
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