[linux-pm] [RFC/PATCH v2] PM / Runtime: allow _put_sync() from interrupts-disabled context

[Kevin Hilman]

"Rafael J. Wysocki" <rjw at sisk.pl> writes:

> On Friday, August 05, 2011, Kevin Hilman wrote:
>> "Rafael J. Wysocki" <rjw at sisk.pl> writes:
>> 
>> > On Friday, July 22, 2011, Kevin Hilman wrote:
>> >> Currently the use of pm_runtime_put_sync() is not safe from
>> >> interrupts-disabled context because rpm_idle() will release the
>> >> spinlock and enable interrupts for the idle callbacks.  This enables
>> >> interrupts during a time where interrupts were expected to be
>> >> disabled, and can have strange side effects on drivers that expected
>> >> interrupts to be disabled.
>> >> 
>> >> This is not a bug since the documentation clearly states that only
>> >> _put_sync_suspend() is safe in IRQ-safe mode.
>> >> 
>> >> However, pm_runtime_put_sync() could be made safe when in IRQ-safe
>> >> mode by releasing the spinlock but not re-enabling interrupts, which
>> >> is what this patch aims to do.
>> >> 
>> >> Problem was found when using some buggy drivers that set
>> >> pm_runtime_irq_safe() and used _put_sync() in interrupts-disabled
>> >> context.
>> >> 
>> >> The offending drivers have been fixed to use _put_sync_suspend(),
>> >> But this patch is an RFC to see if it might make sense to allow
>> >> using _put_sync() from interrupts-disabled context.
>> >
>> > OK, I'm going to take this for 3.2.
>> 
>> Rafael, 
>> 
>> Since you're planning to merge this, maybe we should consider merging
>> this as a fix for v3.1, and possibly even for v3.0 stable.  That way,
>> any current drivers using irq_safe and the normal _put_sync() will not
>> have this problem.
>
> I think I can push it for 3.1, but I don't think it's stable material.
>

OK, fair enough.

Kevin