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 9ac99896db8f13094e253c36e62bfde20a481708..48fc74b6df55aba7195d5bfe25f7b4bf8b2bf531 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;
        }