[PATCH v4 5/6] PM / Runtime: force memory allocation with no I/O during Runtime PM callbcack

[Ming Lei]

This patch applies the introduced memalloc_noio_save() and
memalloc_noio_restore() to force memory allocation with no I/O
during runtime_resume/runtime_suspend callback on device with
the flag of 'memalloc_noio' set.

Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Cc: Oliver Neukum <oneukum@xxxxxxx>
Cc: Rafael J. Wysocki <rjw@xxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
---
v4:
	- runtime_suspend need this too because rpm_resume may wait for
	completion of concurrent runtime_suspend, so deadlock still may
	be triggered in runtime_suspend path.
---
 drivers/base/power/runtime.c |   32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index d477924..7ed17a9 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -368,6 +368,7 @@ static int rpm_suspend(struct device *dev, int rpmflags)
 	int (*callback)(struct device *);
 	struct device *parent = NULL;
 	int retval;
+	unsigned int noio_flag;
 
 	trace_rpm_suspend(dev, rpmflags);
 
@@ -477,7 +478,20 @@ static int rpm_suspend(struct device *dev, int rpmflags)
 	if (!callback && dev->driver && dev->driver->pm)
 		callback = dev->driver->pm->runtime_suspend;
 
-	retval = rpm_callback(callback, dev);
+	/*
+	 * Deadlock might be caused if memory allocation with GFP_KERNEL
+	 * happens inside runtime_suspend callback of one block device's
+	 * ancestor or the block device itself. Network device might be
+	 * thought as part of iSCSI block device, so network device and
+	 * its ancestor should be marked as memalloc_noio.
+	 */
+	if (dev->power.memalloc_noio) {
+		memalloc_noio_save(noio_flag);
+		retval = rpm_callback(callback, dev);
+		memalloc_noio_restore(noio_flag);
+	} else {
+		retval = rpm_callback(callback, dev);
+	}
 	if (retval)
 		goto fail;
 
@@ -560,6 +574,7 @@ static int rpm_resume(struct device *dev, int rpmflags)
 	int (*callback)(struct device *);
 	struct device *parent = NULL;
 	int retval = 0;
+	unsigned int noio_flag;
 
 	trace_rpm_resume(dev, rpmflags);
 
@@ -709,7 +724,20 @@ static int rpm_resume(struct device *dev, int rpmflags)
 	if (!callback && dev->driver && dev->driver->pm)
 		callback = dev->driver->pm->runtime_resume;
 
-	retval = rpm_callback(callback, dev);
+	/*
+	 * Deadlock might be caused if memory allocation with GFP_KERNEL
+	 * happens inside runtime_resume callback of one block device's
+	 * ancestor or the block device itself. Network device might be
+	 * thought as part of iSCSI block device, so network device and
+	 * its ancestor should be marked as memalloc_noio.
+	 */
+	if (dev->power.memalloc_noio) {
+		memalloc_noio_save(noio_flag);
+		retval = rpm_callback(callback, dev);
+		memalloc_noio_restore(noio_flag);
+	} else {
+		retval = rpm_callback(callback, dev);
+	}
 	if (retval) {
 		__update_runtime_status(dev, RPM_SUSPENDED);
 		pm_runtime_cancel_pending(dev);
-- 
1.7.9.5

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