On Wed, Oct 19, 2016 at 05:26:10PM -0700, Brian Norris wrote:
> Consider two devices, A and B, where B is a child of A, and B utilizes
> asynchronous suspend (it does not matter whether A is sync or async). If
> B fails to suspend_noirq() or suspend_early(), or is interrupted by a
> wakeup (pm_wakeup_pending()), then it aborts and sets the async_error
> variable. However, device A does not (immediately) check the async_error
> variable; it may continue to run its own suspend_noirq()/suspend_early()
> callback. This is bad.
>
> We can resolve this problem by checking the async_error flag after
> waiting for children to suspend, using the same logic for the noirq and
> late suspend cases as we already do for __device_suspend().
>
> It's easy to observe this erroneous behavior by, for example, forcing a
> device to sleep a bit in its suspend_noirq() (to ensure the parent is
> waiting for the child to complete), then return an error, and watch the
> parent suspend_noirq() still get called. (Or similarly, fake a wakeup
> event at the right (or is it wrong?) time.)
>
> Fixes: de377b397272 ("PM / sleep: Asynchronous threads for suspend_late")
> Fixes: 28b6fd6e3779 ("PM / sleep: Asynchronous threads for suspend_noirq")
> Reported-by: Jeffy Chen <jeffy.c...@rock-chips.com>
> Signed-off-by: Brian Norris <briannor...@chromium.org>
Makes sense to me.
Reviewed-by: Dmitry Torokhov <dmitry.torok...@gmail.com>
> ---
> Tested mostly on 4.4, but the code (and seemingly the bug) is mostly untouched
> since then. I can try to conjure up a proper upstream test if required.
>
> drivers/base/power/main.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index c58563581345..eaf6b53463a5 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -1040,6 +1040,9 @@ static int __device_suspend_noirq(struct device *dev,
> pm_message_t state, bool a
>
> dpm_wait_for_children(dev, async);
>
> + if (async_error)
> + goto Complete;
> +
> if (dev->pm_domain) {
> info = "noirq power domain ";
> callback = pm_noirq_op(&dev->pm_domain->ops, state);
> @@ -1187,6 +1190,9 @@ static int __device_suspend_late(struct device *dev,
> pm_message_t state, bool as
>
> dpm_wait_for_children(dev, async);
>
> + if (async_error)
> + goto Complete;
> +
> if (dev->pm_domain) {
> info = "late power domain ";
> callback = pm_late_early_op(&dev->pm_domain->ops, state);
> --
> 2.8.0.rc3.226.g39d4020
>
--
Dmitry
