[PATCH] raw1394: fix locking in the presence of SMP and interrupts

Changes all spinlocks that can be held during an irq handler to disable
interrupts while the lock is held.  Changes spin_[un]lock_irq to use the
irqsave/irqrestore variants for robustness and readability.

In raw1394.c:handle_iso_listen(), don't grab host_info_lock at all -- we're
not accessing host_info_list or host_count, and holding this lock while
trying to tasklet_kill the iso tasklet this can cause an ABBA deadlock if
ohci:dma_rcv_tasklet is running and tries to grab host_info_lock in
raw1394.c:receive_iso.  Test program attached reliably deadlocks all SMP
machines I have been able to test without this patch.
Signed-off-by: Andy Wingo <wingo@pobox.com>
Acked-by: Ben Collins <bcollins@ubuntu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/ieee1394/ohci1394.c

@@ -2283,8 +2283,9 @@ static void ohci_schedule_iso_tasklets(struct ti_ohci *ohci,
 {
 	struct ohci1394_iso_tasklet *t;
 	unsigned long mask;
+	unsigned long flags;
 
-	spin_lock(&ohci->iso_tasklet_list_lock);
+	spin_lock_irqsave(&ohci->iso_tasklet_list_lock, flags);
 
 	list_for_each_entry(t, &ohci->iso_tasklet_list, link) {
 		mask = 1 << t->context;
@@ -2295,8 +2296,7 @@ static void ohci_schedule_iso_tasklets(struct ti_ohci *ohci,
 			tasklet_schedule(&t->tasklet);
 	}
 
-	spin_unlock(&ohci->iso_tasklet_list_lock);
-
+	spin_unlock_irqrestore(&ohci->iso_tasklet_list_lock, flags);
 }
 
 static irqreturn_t ohci_irq_handler(int irq, void *dev_id,