linux-kernel - Re: broken suspend (sched related) [Was: 2.6.24-rc4-mm1]

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Message-ID: <c03d1bd00712100349i2c878d94g3085ed78f23c247e@mail.gmail.com>
Date:	Mon, 10 Dec 2007 17:19:43 +0530
From:	"Gautham R Shenoy" <ego.lkml@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Gautham R Shenoy" <ego@...ibm.com>,
	"Jiri Slaby" <jirislaby@...il.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	"Arjan van de Ven" <arjan@...ux.intel.com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Linux-pm mailing list" <linux-pm@...ts.linux-foundation.org>,
	"Dipankar Sarma" <dipankar@...ibm.com>
Subject: Re: broken suspend (sched related) [Was: 2.6.24-rc4-mm1]

On Dec 10, 2007 4:58 PM, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Gautham R Shenoy <ego@...ibm.com> wrote:
>
> > > say we've got 100 CPUs, so we've got 100 watchdog tasks running -
> > > one for each CPU. Checking for hung tasks is a global operation not
> > > a per-CPU operation (we iterate over the global tasklist), hence
> > > only one CPU should really be calling this function. That
> > > online-cpus logic achieves this by picking a single CPU. Perhaps it
> > > would be better to keep a hung_task_checker_cpu variable that is
> > > driven from a CPU-hotplug-down notifier? That way if a CPU is
> > > brought down we can update hung_task_checker_cpu to another,
> > > still-online CPU. (this would also be faster, because event-driven)
> >
> > Do you mean something like this?
>
> yeah, thanks - queued it up.

Stupid me! I forgot to remove the local variable check_cpu in static
int watchdog(void * __bind_cpu). Could you please correct it before
applying?

>
> one question:
>
> > +static int check_cpu = -1;
>
> >       case CPU_ONLINE:
> >       case CPU_ONLINE_FROZEN:
> > +             check_cpu = any_online_cpu(cpu_online_map);
> >               wake_up_process(per_cpu(watchdog_task, hotcpu));
> >               break;
>
> do we bring the boot CPU online too - i.e. will check_cpu be properly
> initialized on UP too?

Yes, it does.
>
>         Ingo
>

Thanks and Regards
gautham.
-- 
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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