• Rafael J. Wysocki's avatar
    DRM / radeon / KMS: Fix hibernation regression related to radeon PM (was: Re:... · 3f53eb6f
    Rafael J. Wysocki authored
    DRM / radeon / KMS: Fix hibernation regression related to radeon PM (was: Re: [Regression, post-2.6.34] Hibernation broken on machines with radeon/KMS and r300)
    
    There is a regression from 2.6.34 related to the recent radeon power
    management changes, caused by attempting to cancel a delayed work
    item that's never been scheduled.  However, the code as is has some
    other issues potentially leading to visible problems.
    
    First, the mutex around cancel_delayed_work() in radeon_pm_suspend()
    doesn't really serve any purpose, because cancel_delayed_work() only
    tries to delete the work's timer.  Moreover, it doesn't prevent the
    work handler from running, so the handler can do some wrong things if
    it wins the race and in that case it will rearm itself to do some
    more wrong things going forward.  So, I think it's better to wait for
    the handler to return in case it's already been queued up for
    execution.  Also, it should be prevented from rearming itself in that
    case.
    
    Second, in radeon_set_pm_method() the cancel_delayed_work() is not
    sufficient to prevent the work handler from running and queing up
    itself for the next run (the failure scenario is that
    cancel_delayed_work() returns 0, so the handler is run, it waits on
    the mutex and then rearms itself after the mutex has been released),
    so again the work handler should be prevented from rearming itself in
    that case..
    
    Finally, there's a potential deadlock in radeon_pm_fini(), because
    cancel_delayed_work_sync() is called under rdev->pm.mutex, but the
    work handler tries to acquire the same mutex (if it wins the race).
    
    Fix the issues described above.
    Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
    Reviewed-by: default avatarAlex Deucher <alexdeucher@gmail.com>
    Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
    3f53eb6f
radeon.h 45 KB