IDE: Fix Power Management request race on resume

PATCH New Benjamin Herrenschmidt 1 participant 1 message Sep 9, 2003

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Benjamin Herrenschmidt

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2003-09-09 18:40 UTC #0 lore raw

PATCH 1/1 IDE: Fix Power Management request race on resume

Hi Linus !

The current IDE Power Management code I wrote has a race on wakeup when the master device got resumed, it may take a request. At this point, a PM resume request to a slave device of the same hwgroup would clear hwgroup->rq and cause an Oops when the master device request completes.

This patch fixes it. Due to the context in which PM resume requests are sent, just not clearing hwgroup->rq for these is enough.

Please apply, this patch was already tested & discussed with Bart.

I also removed a useless debug message in the PM code that was actually misleading (people though it indicated a problem while it didn't, it's really useless) and fix a typo in a comment.

Cheers,
Ben.

drivers/ide/ide-io.c +3 -5

diff -urN linux-2.5/drivers/ide/ide-io.c linuxppc-2.5-benh/drivers/ide/ide-io.c
@@ -928,13 +928,10 @@
 		 * 
 		 * We let requests forced at head of queue with ide-preempt
 		 * though. I hope that doesn't happen too much, hopefully not
-		 * unless the subdriver triggers such a thing in it's own PM
+		 * unless the subdriver triggers such a thing in its own PM
 		 * state machine.
 		 */
 		if (drive->blocked && !blk_pm_request(rq) && !(rq->flags & REQ_PREEMPT)) {
-#ifdef DEBUG_PM
-			printk("%s: a request made it's way while we are power managing...\n", drive->name);
-#endif
 			/* We clear busy, there should be no pending ATA command at this point. */
 			hwgroup->busy = 0;
 			break;

@@ -1417,8 +1414,9 @@
 	}
 
 	spin_lock_irqsave(&ide_lock, flags);
-	if (action == ide_preempt || action == ide_head_wait) {
+	if (action == ide_preempt)
 		hwgroup->rq = NULL;
+	if (action == ide_preempt || action == ide_head_wait) {
 		where = ELEVATOR_INSERT_FRONT;
 		rq->flags |= REQ_PREEMPT;
 	}