On Mon, Oct 15, 2012 at 10:14 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 15 Oct 2012, Ming Lei wrote: > >> 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 <stern@xxxxxxxxxxxxxxxxxxx> >> Cc: Oliver Neukum <oneukum@xxxxxxx> >> Cc: Rafael J. Wysocki <rjw@xxxxxxx> >> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx> >> --- >> 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); > > This is not so good. What happens if I/O was already forbidden when > this function was called? You are right, the old flag should be saved before forbidding and restored after allowing. Thanks, -- Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
