2.6.22-rc1: Broken suspend on SMP with tifm

["Rafael J. Wysocki" <rjw@sisk.pl>]

Hi,

The suspend/hibernation is broken on SMP due to:

commit 3540af8ffddcdbc7573451ac0b5cd57a2eaf8af5
tifm: replace per-adapter kthread with freezeable workqueue

Well, it looks like freezable worqueues still deadlock with CPU hotplug
when worker threads are frozen.

The appended patch fixes the issue, but I think we could even avoid the
killing of frozen worker threads.

Greetings,
Rafael


---
Prevent freezable worqueues from deadlocking with CPU hotplug during a
suspend/hibernation by thawing their worker threads before they get stopped.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 kernel/workqueue.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

Index: linux-2.6.22-rc1/kernel/workqueue.c
===================================================================
--- linux-2.6.22-rc1.orig/kernel/workqueue.c
+++ linux-2.6.22-rc1/kernel/workqueue.c
@@ -799,9 +799,7 @@ static int __devinit workqueue_cpu_callb
 	struct cpu_workqueue_struct *cwq;
 	struct workqueue_struct *wq;
 
-	action &= ~CPU_TASKS_FROZEN;
-
-	switch (action) {
+	switch (action & ~CPU_TASKS_FROZEN) {
 	case CPU_LOCK_ACQUIRE:
 		mutex_lock(&workqueue_mutex);
 		return NOTIFY_OK;
@@ -819,20 +817,29 @@ static int __devinit workqueue_cpu_callb
 
 		switch (action) {
 		case CPU_UP_PREPARE:
+		case CPU_UP_PREPARE_FROZEN:
 			if (!create_workqueue_thread(cwq, cpu))
 				break;
 			printk(KERN_ERR "workqueue for %i failed\n", cpu);
 			return NOTIFY_BAD;
 
 		case CPU_ONLINE:
+		case CPU_ONLINE_FROZEN:
 			start_workqueue_thread(cwq, cpu);
 			break;
 
 		case CPU_UP_CANCELED:
+		case CPU_UP_CANCELED_FROZEN:
 			start_workqueue_thread(cwq, -1);
 		case CPU_DEAD:
 			cleanup_workqueue_thread(cwq, cpu);
 			break;
+
+		case CPU_DEAD_FROZEN:
+			if (wq->freezeable)
+				thaw_process(cwq->thread);
+			cleanup_workqueue_thread(cwq, cpu);
+			break;
 		}
 	}