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>

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 9bc4c00872c927a1033013a31ab19630ba9dc170..24e8ceacc388cd14e9ff4ae87fcc47d6f8d96b2b 100644 (file)
--- 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)