* [v4.2+ regression] fd7a4bed sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks
@ 2015-09-28 2:17 Mike Galbraith
2015-09-29 8:19 ` Mike Galbraith
0 siblings, 1 reply; 3+ messages in thread
From: Mike Galbraith @ 2015-09-28 2:17 UTC (permalink / raw)
To: Peter Zijlstra; +Cc: Ingo Molnar, LKML
Hi Peter,
I bumped into an odd futextest regression, and finally bisected it to
$subject. I haven't poked at it yet, chasing down and confirming the
little bugger munched the day.
#!/bin/sh
cd /home/git/futextest/functional
trap "killall -KILL -q cpuhog;exit;" INT
for i in `seq 0 7`; do taskset -c $i cpuhog& done
sleep 1
for i in `seq 1000`
do
echo iteration $i
./futex_requeue_pi -c -b -o -t 500000
done
killall cpuhog
Without the cpuhogs, it won't hang.
-Mike
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [v4.2+ regression] fd7a4bed sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks
2015-09-28 2:17 [v4.2+ regression] fd7a4bed sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks Mike Galbraith
@ 2015-09-29 8:19 ` Mike Galbraith
2015-09-29 8:55 ` Peter Zijlstra
0 siblings, 1 reply; 3+ messages in thread
From: Mike Galbraith @ 2015-09-29 8:19 UTC (permalink / raw)
To: Peter Zijlstra, Darren Hart; +Cc: Ingo Molnar, LKML
On Mon, 2015-09-28 at 04:17 +0200, Mike Galbraith wrote:
> Hi Peter,
>
> I bumped into an odd futextest regression, and finally bisected it to
> $subject. I haven't poked at it yet, chasing down and confirming the
> little bugger munched the day.
homer:/home/git/futextest/functional # ./futex_requeue_pi -c -b -o -t 500000 -v 2 2>&1|egrep 'exit|Blocker'
INFO: Waiter 0: exiting with 0
INFO: Waiter 1: exiting with 0
INFO: Waiter 2: exiting with 0
INFO: Waiter 3: exiting with 0
INFO: Waiter 4: exiting with 0
INFO: Waiter 5: exiting with 0
INFO: Waiter 6: exiting with 0
INFO: Waiter 7: exiting with 0
INFO: Waiter 8: exiting with 0
INFO: Waiter 9: exiting with 0
INFO: Waker: exiting with 0
INFO: Blocker: Calling futex_wait()
Well now, it _seems_ you're innocent Peter. Waker can call futex_wake()
before blocker calls futex_wait(), leaving poor blocker stranded.
Adding atomic_inc(&waiters_blocked) to blocker, and telling wakers to
expect one more when a blocker exists seems to have fixed it up.
-Mike
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [v4.2+ regression] fd7a4bed sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks
2015-09-29 8:19 ` Mike Galbraith
@ 2015-09-29 8:55 ` Peter Zijlstra
0 siblings, 0 replies; 3+ messages in thread
From: Peter Zijlstra @ 2015-09-29 8:55 UTC (permalink / raw)
To: Mike Galbraith; +Cc: Darren Hart, Ingo Molnar, LKML
On Tue, Sep 29, 2015 at 10:19:51AM +0200, Mike Galbraith wrote:
> On Mon, 2015-09-28 at 04:17 +0200, Mike Galbraith wrote:
> > Hi Peter,
> >
> > I bumped into an odd futextest regression, and finally bisected it to
> > $subject. I haven't poked at it yet, chasing down and confirming the
> > little bugger munched the day.
> Well now, it _seems_ you're innocent Peter.
Whee! thanks for looking.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2015-09-29 9:00 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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2015-09-28 2:17 [v4.2+ regression] fd7a4bed sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks Mike Galbraith
2015-09-29 8:19 ` Mike Galbraith
2015-09-29 8:55 ` Peter Zijlstra
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