linux-kernel - Re: [PATCH] powerpc: secondary CPUs signal to master before setting active and online (fixes kernel BUG at kernel/smpboot.c:134!)

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Message-ID: <1418252789.26146.0.camel@ellerman.id.au>
Date:	Thu, 11 Dec 2014 10:06:29 +1100
From:	Michael Ellerman <mpe@...erman.id.au>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Anton Blanchard <anton@...ba.org>, Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Tejun Heo <tj@...nel.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	yuyang.du@...el.com, lkp@...org,
	Yuanhan Liu <yuanhan.liu@...ux.intel.com>,
	Paul Turner <pjt@...gle.com>,
	Benjamin Segall <bsegall@...gle.com>,
	Daniel J Blueman <daniel@...ascale.com>,
	subbaram@...eaurora.org,
	Brian Norris <computersforpeace@...il.com>,
	Slava Pestov <sp@...era.io>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH] powerpc: secondary CPUs signal to master before setting
 active and online (fixes kernel BUG at kernel/smpboot.c:134!)

On Tue, 2014-12-09 at 12:54 -0800, Linus Torvalds wrote:
> On Mon, Dec 8, 2014 at 3:58 PM, Anton Blanchard <anton@...ba.org> wrote:
> > Hi Ingo,
> >
> >> At that point I thought the previous task_cpu() was somewhat ingrained
> >> in the scheduler and came up with the patch. If not, we could go on a
> >> hunt to see what else needs fixing.
> >
> > I had another look. The scheduled does indeed make assumptions about the
> > previous task_cpu, but we have a hammer to fix it up called
> > select_fallback_rq.
> >
> > I annotated select_fallback_rq, and did hit a case where the CPU was
> > not active. ppc64 patch below.
> 
> Anton, I'll assume I will get this through the usual powerpc pull requests?

Yeah I'll put it in my tree unless Anton objects.

cheers


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