From: Peter Zijlstra <peterz@infradead.org>
To: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: deadlock in scheduler enabling HRTICK feature
Date: Fri, 28 Jun 2013 11:09:39 +0200 [thread overview]
Message-ID: <20130628090939.GD29209@dyad.programming.kicks-ass.net> (raw)
In-Reply-To: <51CCBCA9.1000200@gmail.com>
On Thu, Jun 27, 2013 at 04:28:57PM -0600, David Ahern wrote:
> On 6/27/13 4:43 AM, Peter Zijlstra wrote:
> >On Wed, Jun 26, 2013 at 10:46:33AM -0600, David Ahern wrote:
> >>On 6/26/13 1:05 AM, Peter Zijlstra wrote:
> >>>>What is the expectation that the feature provides? not a whole lot of
> >>>>documentation on it. I walked down the path wondering if it solved an odd
> >>>>problem we are seeing with the CFS in 2.6.27 kernel.
> >>>
> >>>Its supposed to use hrtimers for slice expiry instead of the regular tick.
> >>
> >>So theoretically CPU bound tasks would get preempted sooner? That was my
> >>guess/hope anyways.
> >
> >Doth the below worketh?
>
> It doth.
>
> Usually make -j 8 for a kernel build in a VM would lock it up pretty
> quickly. With the patch I was able to run full builds multiple times.
Good!
> As for the solution you are avoiding the nesting by not waking up the
> softirq daemon.
Yah! :-) Obviously doing a wakeup while holding scheduler locks isn't going to
work out well. And the only reason we really need that pesky softirq nonsense
is when we accidentally schedule a timer that's already expired; in that case
we'll run it from sirq context.
We don't care about missing events like that; there's always the actual tick
for backup.
I suppose I'd better go write a Changelog and properly submit the patch :-)
next prev parent reply other threads:[~2013-06-28 9:10 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-25 21:05 deadlock in scheduler enabling HRTICK feature David Ahern
2013-06-25 21:17 ` Peter Zijlstra
2013-06-25 21:20 ` David Ahern
2013-06-26 7:05 ` Peter Zijlstra
2013-06-26 16:46 ` David Ahern
2013-06-27 10:43 ` Peter Zijlstra
2013-06-27 10:53 ` Peter Zijlstra
2013-06-27 12:28 ` Mike Galbraith
2013-06-27 13:06 ` Ingo Molnar
2013-06-27 19:18 ` Andy Lutomirski
2013-06-27 20:37 ` Peter Zijlstra
2013-06-27 22:28 ` David Ahern
2013-06-28 9:00 ` Ingo Molnar
2013-06-28 9:18 ` Peter Zijlstra
2013-07-12 13:29 ` [tip:sched/core] sched: Fix HRTICK tip-bot for Peter Zijlstra
2013-06-28 9:09 ` Peter Zijlstra [this message]
2013-06-28 17:28 ` deadlock in scheduler enabling HRTICK feature David Ahern
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