linux-kernel - [078/107] PCI / PM: Block races between runtime PM and system sleep

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Date:	Thu, 07 Jul 2011 17:16:50 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: [078/107] PCI / PM: Block races between runtime PM and system sleep

2.6.39-stable review patch.  If anyone has any objections, please let us know.

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

From: "Rafael J. Wysocki" <rjw@...k.pl>

commit a5f76d5eba157bf637beb2dd18026db2917c512e upstream.

After commit e8665002477f0278f84f898145b1f141ba26ee26
(PM: Allow pm_runtime_suspend() to succeed during system suspend) it
is possible that a device resumed by the pm_runtime_resume(dev) in
pci_pm_prepare() will be suspended immediately from a work item,
timer function or otherwise, defeating the very purpose of calling
pm_runtime_resume(dev) from there.  To prevent that from happening
it is necessary to increment the runtime PM usage counter of the
device by replacing pm_runtime_resume() with pm_runtime_get_sync().
Moreover, the incremented runtime PM usage counter has to be
decremented by the corresponding pci_pm_complete(), via
pm_runtime_put_sync().

Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
Acked-by: Jesse Barnes <jbarnes@...tuousgeek.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/pci/pci-driver.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -624,7 +624,7 @@ static int pci_pm_prepare(struct device
 	 * system from the sleep state, we'll have to prevent it from signaling
 	 * wake-up.
 	 */
-	pm_runtime_resume(dev);
+	pm_runtime_get_sync(dev);

 	if (drv && drv->pm && drv->pm->prepare)
 		error = drv->pm->prepare(dev);
@@ -638,6 +638,8 @@ static void pci_pm_complete(struct devic

 	if (drv && drv->pm && drv->pm->complete)
 		drv->pm->complete(dev);
+
+	pm_runtime_put_sync(dev);
 }

 #else /* !CONFIG_PM_SLEEP */

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