This patch applies the introduces tsk_memalloc_forbid_io() and
tsk_memalloc_allow_io() to force memory allocation with no I/O
during runtime_resume callback.
Cc: Alan Stern <st...@rowland.harvard.edu>
Cc: Oliver Neukum <oneu...@suse.de>
Cc: Rafael J. Wysocki <r...@sisk.pl>
Signed-off-by: Ming Lei <ming....@canonical.com>
---
drivers/base/power/runtime.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 3148b10..76836c1 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -652,7 +652,20 @@ static int rpm_resume(struct device *dev, int rpmflags)
if (!callback && dev->driver && dev->driver->pm)
callback = dev->driver->pm->runtime_resume;
+ /*
+ * 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. The easiest approach is
+ * to forbid I/O inside runtime_resume of all devices.
+ *
+ * In fact, it can be done only if the deivce is a block device
+ * or there is one block device descendant. But that may become
+ * complicated and not efficient because device tree traversing
+ * is involved.
+ */
+ tsk_memalloc_forbid_io(current);
retval = rpm_callback(callback, dev);
+ tsk_memalloc_allow_io(current);
if (retval) {
__update_runtime_status(dev, RPM_SUSPENDED);
pm_runtime_cancel_pending(dev);
--
1.7.9.5
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