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Date: Thu, 24 Nov 2016 15:55:44 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Jeffy Chen <jeffy.chen@...k-chips.com>, Brian Norris <briannorris@...omium.org>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com> Subject: [PATCH 4.4 23/31] PM / sleep: dont suspend parent when async child suspend_{noirq, late} fails 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Brian Norris <briannorris@...omium.org> commit 6f75c3fd56daf547d684127a7f83c283c3c160d1 upstream. 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_late(), 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_late() callback. This is bad. We can resolve this problem by doing our error and wakeup checking (particularly, for the async_error flag) after waiting for children to suspend, instead of before. This also helps align the logic for the noirq and late suspend cases with the logic in __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.chen@...k-chips.com> Signed-off-by: Brian Norris <briannorris@...omium.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- drivers/base/power/main.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/drivers/base/power/main.c +++ b/drivers/base/power/main.c @@ -1022,6 +1022,8 @@ static int __device_suspend_noirq(struct TRACE_DEVICE(dev); TRACE_SUSPEND(0); + dpm_wait_for_children(dev, async); + if (async_error) goto Complete; @@ -1033,8 +1035,6 @@ static int __device_suspend_noirq(struct if (dev->power.syscore || dev->power.direct_complete) goto Complete; - dpm_wait_for_children(dev, async); - if (dev->pm_domain) { info = "noirq power domain "; callback = pm_noirq_op(&dev->pm_domain->ops, state); @@ -1169,6 +1169,8 @@ static int __device_suspend_late(struct __pm_runtime_disable(dev, false); + dpm_wait_for_children(dev, async); + if (async_error) goto Complete; @@ -1180,8 +1182,6 @@ static int __device_suspend_late(struct if (dev->power.syscore || dev->power.direct_complete) goto Complete; - dpm_wait_for_children(dev, async); - if (dev->pm_domain) { info = "late power domain "; callback = pm_late_early_op(&dev->pm_domain->ops, state);
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