Re: [PATCH] PM: Acquire device locks on suspend

On Sunday, 6 of January 2008, Rafael J. Wysocki wrote:

On Sunday, 6 of January 2008, Rafael J. Wysocki wrote:

quoted

On Sunday, 6 of January 2008, Alan Stern wrote:

quoted

On Sun, 6 Jan 2008, Rafael J. Wysocki wrote:

quoted

quoted

If you can figure out a way to disable the warning in device_del() for 
just the one device being unregistered by 
device_pm_destroy_suspended(),

Something like this, perhaps:

@@ -905,6 +915,18 @@ void device_del(struct device * dev)
 	struct device * parent = dev->parent;
 	struct class_interface *class_intf;
 
+	if (down_trylock(&dev->sem)) {
+		if (pm_sleep_lock()) {
+			dev_warn(dev, "Illegal %s during suspend\n",
+				__FUNCTION__);
+			dump_stack();
+		} else {
+			pm_sleep_unlock();
+		}
+	} else {
+		up(&dev->sem);
+	}
+
 	if (parent)
 		klist_del(&dev->knode_parent);
 	if (MAJOR(dev->devt))

Bizarre, but it should work.

OK

Still, shouldn't we fail the removal of the device apart from giving the
warning?

Actually, having thought about it a bit more, I don't see the point in
preventing the removal of the device from the list in device_pm_remove() if
we allow all of the operations in device_del() preceding it to be performed.

Shouldn't we just take pm_sleep_rwsem in device_del() upfront and block on that
if locked?

Ugh, the $subject patch looks like a city of races.  I'm struggling to close
them all, but it's getting complicated.

I'll post the result in a new thread.

Thanks,
Rafael