On Friday, September 03, 2010, Colin Cross wrote:
> During suspend, the power.completion is expected to be set when a
> device has not yet started suspending. Set it on init to fix a
> corner case where a device is resumed when its parent has never
> suspended.
>
> Consider three drivers, A, B, and C. The parent of A is C, and C
> has async_suspend set. On boot, C->power.completion is initialized
> to 0.
>
> During the first suspend:
> suspend_devices_and_enter(...)
> dpm_resume(...)
> device_suspend(A)
> device_suspend(B) returns error, aborts suspend
> dpm_resume_end(...)
> dpm_resume(...)
> device_resume(A)
> dpm_wait(A->parent == C)
> wait_for_completion(C->power.completion)
>
> The wait_for_completion will never complete, because
> complete_all(C->power.completion) will only be called from
> device_suspend(C) or device_resume(C), neither of which is called
> if suspend is aborted before C.
>
> After a successful suspend->resume cycle, where B doesn't abort
> suspend, C->power.completion is left in the completed state by the
> call to device_resume(C), and the same call path will work if B
> aborts suspend.
>
> Signed-off-by: Colin Cross <ccross@xxxxxxxxxxx>
Thanks, rebased on top of the current Linus' tree and applied to
suspend-2.6/pm-fixes .
Rafael
> ---
> drivers/base/power/main.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index cb784a0..b1b4029 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -63,6 +63,7 @@ void device_pm_init(struct device *dev)
> {
> dev->power.status = DPM_ON;
> init_completion(&dev->power.completion);
> + complete_all(&dev->power.completion);
> pm_runtime_init(dev);
> }
>
>
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