Re: [PATCH][GIT PULL] tracing: Fix compile issue for trace_sched_wakeup.c

Peter Zijlstra
2010-10-22T08:14:44Z

On Thu, 2010-10-21 at 21:44 -0400, Jason Baron wrote:

> I finally found that we actually continue to run after the above
> apparent 'hang'. That is, we continue to make progress updating the jump
> labels. And doing a dump of all the system tasks at the time of the hang
> showed the processes in various places besides the stop machine threads.
> Thus, I thought that perhaps, for some reason the stop machine threads
> weren't being scheduled.
>
> Thus, I tried commenting out the special scheduling that is set up for
> stop machine threads, and that fixed the hang. I haven't yet looked into
> what might be going wrong with that scheduling...but maybe somebody else
> knows...

Hrmm, so are you saying rq->stop was runnable but not running?

That would imply broken wakeup-preemption, does something like the below
cure that?

---
kernel/sched_stoptask.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/kernel/sched_stoptask.c b/kernel/sched_stoptask.c
index 45bddc0..50ad10f 100644
--- a/kernel/sched_stoptask.c
+++ b/kernel/sched_stoptask.c
@@ -35,6 +35,7 @@ static struct task_struct *pick_next_task_stop(struct rq *rq)
static void
enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
{
+ resched_cpu(cpu_of(rq));
}

static void