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

"Rafael J. Wysocki" [off-list ref] writes:

On Friday, August 05, 2011, Kevin Hilman wrote:

quoted

"Rafael J. Wysocki" [off-list ref] writes:

quoted

On Friday, July 22, 2011, Kevin Hilman wrote:

quoted

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