stop_machine: fix race with return value (fixes Bug #11989)

Bug #11989: Suspend failure on NForce4-based boards due to chanes in
stop_machine

We should not access active.fnret outside the lock; in theory the next
stop_machine could overwrite it.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Tested-by: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 9bc4c00872c9..24e8ceacc388 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -112,7 +112,7 @@ static int chill(void *unused)
 int __stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus)
 {
         struct work_struct *sm_work;
-        int i;
+        int i, ret;
 
         /* Set up initial state. */
         mutex_lock(&lock);
@@ -137,8 +137,9 @@ int __stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus)
         /* This will release the thread on our CPU. */
         put_cpu();
         flush_workqueue(stop_machine_wq);
+        ret = active.fnret;
         mutex_unlock(&lock);
-        return active.fnret;
+        return ret;
 }
 
 int stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus)