From: Mike Galbraith <efault@gmx.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Sachin Sant <sachinp@linux.vnet.ibm.com>,
Ross Zwisler <zwisler@gmail.com>,
Matt Fleming <matt@codeblueprint.co.uk>,
Michael Ellerman <mpe@ellerman.id.au>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"linux-next@vger.kernel.org" <linux-next@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Paul McKenney <paulmck@linux.vnet.ibm.com>
Subject: Re: [tip:sched/core] sched/core: Add debugging code to catch missing update_rq_clock() calls
Date: Fri, 03 Feb 2017 14:52:35 +0100 [thread overview]
Message-ID: <1486129955.3993.6.camel@gmx.de> (raw)
In-Reply-To: <20170203133748.GB6515@twins.programming.kicks-ass.net>
On Fri, 2017-02-03 at 14:37 +0100, Peter Zijlstra wrote:
> On Fri, Feb 03, 2017 at 01:59:34PM +0100, Mike Galbraith wrote:
> > FWIW, I'm not seeing stalls/hangs while beating hotplug up in tip. (so
> > next grew a wart?)
>
> I've seen it on tip. It looks like hot unplug goes really slow when
> there's running tasks on the CPU being taken down.
>
> What I did was something like:
>
> taskset -p $((1<<1)) $$
> for ((i=0; i<20; i++)) do while :; do :; done & done
>
> taskset -p $((1<<0)) $$
> echo 0 > /sys/devices/system/cpu/cpu1/online
>
> And with those 20 tasks stuck sucking cycles on CPU1, the unplug goes
> _really_ slow and the RCU stall triggers. What I suspect happens is that
> hotplug stops participating in the RCU state machine early, but only
> tells RCU about it really late, and in between it gets suspicious it
> takes too long.
Ah. I wasn't doing a really hard pounding, just running a couple
instances of Steven's script. To beat hell out of it, I add futextest,
stockfish and a small kbuild on a big box.
-Mike
next prev parent reply other threads:[~2017-02-03 13:53 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-21 13:38 [PATCH v2 0/7] sched: Diagnostic checks for missing rq clock updates Matt Fleming
2016-09-21 13:38 ` [PATCH v2 1/7] sched/fair: Update the rq clock before detaching tasks Matt Fleming
2016-10-03 12:49 ` Peter Zijlstra
2016-10-03 14:37 ` Matt Fleming
2016-10-03 14:42 ` Peter Zijlstra
2016-09-21 13:38 ` [PATCH v2 2/7] sched/fair: Update rq clock before waking up new task Matt Fleming
2016-09-21 13:38 ` [PATCH v2 3/7] sched/fair: Update rq clock in task_hot() Matt Fleming
2016-09-21 13:38 ` [PATCH v2 4/7] sched: Add wrappers for lockdep_(un)pin_lock() Matt Fleming
2017-01-14 12:40 ` [tip:sched/core] sched/core: " tip-bot for Matt Fleming
2016-09-21 13:38 ` [PATCH v2 5/7] sched/core: Reset RQCF_ACT_SKIP before unpinning rq->lock Matt Fleming
2017-01-14 12:41 ` [tip:sched/core] " tip-bot for Matt Fleming
2016-09-21 13:38 ` [PATCH v2 6/7] sched/fair: Push rq lock pin/unpin into idle_balance() Matt Fleming
2017-01-14 12:41 ` [tip:sched/core] " tip-bot for Matt Fleming
2016-09-21 13:38 ` [PATCH v2 7/7] sched/core: Add debug code to catch missing update_rq_clock() Matt Fleming
2016-09-21 15:58 ` Petr Mladek
2016-09-21 19:08 ` Matt Fleming
2016-09-21 19:46 ` Thomas Gleixner
2016-09-22 0:44 ` Sergey Senozhatsky
2016-09-22 8:04 ` Peter Zijlstra
2016-09-22 8:36 ` Jan Kara
2016-09-22 9:39 ` Peter Zijlstra
2016-09-22 10:17 ` Peter Zijlstra
2017-01-14 12:44 ` [tip:sched/core] sched/core: Add debugging code to catch missing update_rq_clock() calls tip-bot for Matt Fleming
[not found] ` <87tw8gutp6.fsf@concordia.ellerman.id.au>
2017-01-30 21:34 ` Matt Fleming
2017-01-31 8:35 ` Michael Ellerman
2017-01-31 11:00 ` Sachin Sant
2017-01-31 11:48 ` Mike Galbraith
2017-01-31 17:22 ` Ross Zwisler
2017-02-02 15:55 ` Peter Zijlstra
2017-02-02 22:01 ` Matt Fleming
2017-02-03 3:05 ` Mike Galbraith
2017-02-03 4:33 ` Sachin Sant
2017-02-03 8:53 ` Peter Zijlstra
2017-02-03 12:59 ` Mike Galbraith
2017-02-03 13:37 ` Peter Zijlstra
2017-02-03 13:52 ` Mike Galbraith [this message]
2017-02-03 15:44 ` Paul E. McKenney
2017-02-03 15:54 ` Paul E. McKenney
2017-02-06 6:23 ` Sachin Sant
2017-02-06 15:10 ` Paul E. McKenney
2017-02-06 15:14 ` Paul E. McKenney
2017-02-03 13:04 ` Borislav Petkov
2017-02-22 9:03 ` Wanpeng Li
2017-02-24 9:16 ` [tip:sched/urgent] sched/core: Fix update_rq_clock() splat on hotplug (and suspend/resume) tip-bot for Peter Zijlstra
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