sched: fix rt ptracer monopolizing CPU

yield() in wait_task_inactive(), can cause a high priority thread to be
scheduled back in, and there by loop forever while it is waiting for some
lower priority thread which is unfortunately still on the runqueue.

Use schedule_timeout_uninterruptible(1) instead.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Credit: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index 9ac9989..48fc74b 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1133,7 +1133,7 @@ repeat:
         * yield - it could be a while.
         */
        if (unlikely(on_rq)) {
-               yield();
+               schedule_timeout_uninterruptible(1);
                goto repeat;
        }