linux-kernel - Re: Bisection: Lost wakeups from b5179ac70de8

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Message-ID: <20160524090455.GF3192@twins.programming.kicks-ass.net>
Date:	Tue, 24 May 2016 11:04:55 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mgalbraith@...e.de, ahh@...gle.com,
	bsegall@...gle.com, torvalds@...ux-foundation.org,
	matt@...eblueprint.co.uk, morten.rasmussen@....com, pjt@...gle.com,
	pkondeti@...radead.org, tglx@...utronix.de, byungchul.park@....com,
	mingo@...nel.org, rgkernel@...il.com
Subject: Re: Bisection: Lost wakeups from b5179ac70de8

On Mon, May 23, 2016 at 07:04:10AM -0700, Paul E. McKenney wrote:
> Hello, Peter,
> 
> Current mainline doesn't do well with RCU torture testing, and the
> symptom once again looks like lost wakeups.  Thankfully, this time each
> run takes only about an hour, and the false-positive/-negative rate
> is negligible.  This means that for the first time ever, "git bisect"
> actually did something useful for me.  The first bad commit is:
> 
> b5179ac70de8 ("sched/fair: Prepare to fix fairness problems on migration").
> 

Yeah, we have a patch for that.. I'll go writes a Changelog for it and
put it to sched/urgent.

See lkml.kernel.org/r/20160523091907.GD15728@...ktop.ger.corp.intel.com