2008-07-30 17:07:25

by Oleg Nesterov

Subject: [PATCH 1/3] wait_task_inactive: "improve" the returned value for ->nvcsw == 0

(on top of wait_task_inactive-dont-consider-task-nivcsw.patch)

wait_task_inactive() returns 1 when p->nvcsw == 0 || p->nvcsw == 1.
This means that two subsequent calls can return the same number while
the task was scheduled in between.

Change the code to return "nvcsw | LONG_MIN" instead of "nvcsw ?: 1",
now the overlap always needs LONG_MAX schedules.

Signed-off-by: Oleg Nesterov <[email protected]>

--- 27/kernel/sched.c~1_WTI_RET 2008-07-30 19:32:09.000000000 +0400
+++ 27/kernel/sched.c 2008-07-30 19:47:56.000000000 +0400
@@ -1923,7 +1923,7 @@ unsigned long wait_task_inactive(struct
on_rq = p->se.on_rq;
ncsw = 0;
if (!match_state || p->state == match_state)
- ncsw = p->nvcsw ?: 1;
+ ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
task_rq_unlock(rq, &flags);

/*

2008-07-31 00:38:19

by Roland McGrath

Subject: Re: [PATCH 1/3] wait_task_inactive: "improve" the returned value for ->nvcsw == 0

Acked-by: Roland McGrath <[email protected]>


Thanks,
Roland