linux-kernel - Re: [tip:sched/core] sched/core: Add debugging code to catch missing update_rq

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Message-ID: <20170203085301.GA6515@twins.programming.kicks-ass.net>
Date:   Fri, 3 Feb 2017 09:53:01 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Sachin Sant <sachinp@...ux.vnet.ibm.com>
Cc:     Ross Zwisler <zwisler@...il.com>, Mike Galbraith <efault@....de>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Michael Ellerman <mpe@...erman.id.au>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [tip:sched/core] sched/core: Add debugging code to catch missing
 update_rq_clock() calls

On Fri, Feb 03, 2017 at 10:03:14AM +0530, Sachin Sant wrote:
> 
> > On 02-Feb-2017, at 9:25 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > On Tue, Jan 31, 2017 at 10:22:47AM -0700, Ross Zwisler wrote:
> >> On Tue, Jan 31, 2017 at 4:48 AM, Mike Galbraith <efault@....de> wrote:
> >>> On Tue, 2017-01-31 at 16:30 +0530, Sachin Sant wrote:
> > 
> > 
> > Could some of you test this? It seems to cure things in my (very)
> > limited testing.
> > 
> 
> I ran few cycles of cpu hot(un)plug tests. In most cases it works except one
> where I ran into rcu stall:
> 
> [  173.493453] INFO: rcu_sched detected stalls on CPUs/tasks:
> [  173.493473] 	8-...: (2 GPs behind) idle=006/140000000000000/0 softirq=0/0 fqs=2996 
> [  173.493476] 	(detected by 0, t=6002 jiffies, g=885, c=884, q=6350)

Right, I actually saw that too, but I don't think that would be related
to my patch. I'll see if I can dig into this though, ought to get fixed
regardless.

Thanks for testing!