linux-kernel - [ 42/78] PM / Runtime: dont forget to wake up waitqueue on failure

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Date:	Wed, 11 Apr 2012 16:11:00 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Alan Stern <stern@...land.harvard.edu>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: [ 42/78] PM / Runtime: dont forget to wake up waitqueue on failure

3.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alan Stern <stern@...land.harvard.edu>

commit f2791d733a2f06997b573d1a3cfde21e6f529826 upstream.

This patch (as1535) fixes a bug in the runtime PM core.  When a
runtime suspend attempt completes, whether successfully or not, the
device's power.wait_queue is supposed to be signalled.  But this
doesn't happen in the failure pathway of rpm_suspend() when another
autosuspend attempt is rescheduled.  As a result, a task can get stuck
indefinitely on the wait queue (I have seen this happen in testing).

The patch fixes the problem by moving the wake_up_all() call up near
the start of the failure code.

Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/base/power/runtime.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -532,6 +532,8 @@ static int rpm_suspend(struct device *de
 	dev->power.suspend_time = ktime_set(0, 0);
 	dev->power.max_time_suspended_ns = -1;
 	dev->power.deferred_resume = false;
+	wake_up_all(&dev->power.wait_queue);
+
 	if (retval == -EAGAIN || retval == -EBUSY) {
 		dev->power.runtime_error = 0;

@@ -547,7 +549,6 @@ static int rpm_suspend(struct device *de
 	} else {
 		pm_runtime_cancel_pending(dev);
 	}
-	wake_up_all(&dev->power.wait_queue);
 	goto out;
 }

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