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SubjectRe: [ 42/78] PM / Runtime: dont forget to wake up waitqueue on failure
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On Wed, 2012-04-11 at 16:11 -0700, Greg KH wrote:
> 3.3-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Alan Stern <stern@rowland.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.
[...]

It looks like this is also relevant to 3.2, but the code got moved
around a bit between 3.2 and 3.3. Attaching my (untested) backport.

Ben.

--
Ben Hutchings
It is easier to change the specification to fit the program than vice versa.
From 3853eee3a7aae2eda1bb8f9f0c9b8226cbba4bfb Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@rowland.harvard.edu>
Date: Mon, 26 Mar 2012 22:46:52 +0200
Subject: [PATCH] PM / Runtime: don't forget to wake up waitqueue on failure

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@rowland.harvard.edu>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
[bwh: Backported to 3.2: adjust context and indentation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/base/power/runtime.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 8c78443..2424be5 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -417,6 +417,8 @@ static int rpm_suspend(struct device *dev, int rpmflags)
if (retval) {
__update_runtime_status(dev, RPM_ACTIVE);
dev->power.deferred_resume = false;
+ wake_up_all(&dev->power.wait_queue);
+
if (retval == -EAGAIN || retval == -EBUSY) {
dev->power.runtime_error = 0;

@@ -432,7 +434,6 @@ static int rpm_suspend(struct device *dev, int rpmflags)
} else {
pm_runtime_cancel_pending(dev);
}
- wake_up_all(&dev->power.wait_queue);
goto out;
}
no_callback:
--
1.7.9.5
[unhandled content-type:application/pgp-signature]
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