From: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Noticed that migration_thread can examine "kthread_should_stop()?" without
setting its state to TASK_INTERRUPTIBLE first. This can cause kthread_stop
on that thread to block forever ...
P.S - I assumed that having the task state set to TASK_INTERRUTIBLE
while it is doing active_load_balance is fine. It seemed to be
the case earlier also.
---
25-akpm/kernel/sched.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletion(-)
diff -puN kernel/sched.c~sched-kthread_stop_race_fix kernel/sched.c
--- 25/kernel/sched.c~sched-kthread_stop_race_fix 2004-04-30 20:06:34.133124360 -0700
+++ 25-akpm/kernel/sched.c 2004-04-30 20:06:34.138123600 -0700
@@ -3379,6 +3379,7 @@ static int migration_thread(void * data)
rq = cpu_rq(cpu);
BUG_ON(rq->migration_thread != current);
+ set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
struct list_head *head;
migration_req_t *req;
@@ -3400,10 +3401,10 @@ static int migration_thread(void * data)
head = &rq->migration_queue;
- current->state = TASK_INTERRUPTIBLE;
if (list_empty(head)) {
spin_unlock_irq(&rq->lock);
schedule();
+ set_current_state(TASK_INTERRUPTIBLE);
continue;
}
req = list_entry(head->next, migration_req_t, list);
@@ -3424,6 +3425,7 @@ static int migration_thread(void * data)
complete(&req->done);
}
+ __set_current_state(TASK_RUNNING);
return 0;
wait_to_die:
_