On Tue, 16 Jun 2009 16:22:17 +0200
Johannes Stezenbach <js@xxxxxxxxx> wrote:
> Fix swsusp failure on !SMP
>
> Commit 01599fca6758d2cd133e78f87426fc851c9ea725 introduced
> a regression which caused a backtrace on suspend and
> a hang on resume on a Thinkpad T42p (Pentium M CPU).
>
> Signed-off-by: Johannes Stezenbach <js@xxxxxxxxx>
>
>
> --- linux-2.6.30/kernel/up.c.orig 2009-06-16 15:56:28.000000000 +0200
> +++ linux-2.6.30/kernel/up.c 2009-06-16 15:57:27.000000000 +0200
> @@ -10,11 +10,13 @@
> int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
> int wait)
> {
> + unsigned long flags;
> +
> WARN_ON(cpu != 0);
>
> - local_irq_disable();
> + local_irq_save(flags);
> (func)(info);
> - local_irq_enable();
> + local_irq_restore(flags);
>
> return 0;
> }
ok, what's going on here? The patch implies that someone (presumably
acpi-cpufreq) is calling smp_call_function_single() with local
interrupts disabled. That's a bug on SMP kernels. And it'll generate
a trace if it happens:
/* Can deadlock when called with interrupts disabled */
WARN_ON_ONCE(irqs_disabled() && !oops_in_progress);
but nobody has reported such a trace AFAIK?
Also, prior to 01599fca6758d2cd133e78f87426fc851c9ea725, acpi-cpufreq
was using work_on_cpu(). If it was calling work_on_cpu() with local
interrupts disabled then that would have been a bug too, which could
generate might_sleep() or scheduling-while-atomic warnings.
Because it is a bug to call the SMP version of
smp_call_function_single() with local interrupts disabled, I don't
think we should need to apply the above patch.
But I don't know what we _should_ do because I don't know what the bug
is. Are you able to get us a copy of that stack trace?
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