From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753720Ab1HAJzQ (ORCPT ); Mon, 1 Aug 2011 05:55:16 -0400 Received: from casper.infradead.org ([85.118.1.10]:35507 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753088Ab1HAJzM (ORCPT ); Mon, 1 Aug 2011 05:55:12 -0400 Subject: Re: [PATCH] perf: powerpc: Disable pagefaults during callchain stack read From: Peter Zijlstra To: David Ahern Cc: benh@kernel.crashing.org, anton@samba.org, acme@ghostprotocols.net, mingo@elte.hu, paulus@samba.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org In-Reply-To: <1312059200-11563-1-git-send-email-dsahern@gmail.com> References: <1312059200-11563-1-git-send-email-dsahern@gmail.com> Content-Type: text/plain; charset="UTF-8" Date: Mon, 01 Aug 2011 11:59:52 +0200 Message-ID: <1312192792.2617.381.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2011-07-30 at 14:53 -0600, David Ahern wrote: > A page fault occurred walking the callchain while creating a perf > sample for the context-switch event. To handle the page fault the > mmap_sem is needed, but it is currently held by setup_arg_pages. > (setup_arg_pages calls shift_arg_pages with the mmap_sem held. > shift_arg_pages then calls move_page_tables which has a cond_resched > at the top of its for loop - hitting that cond_resched is what caused > the context switch.) > > This is an extension of Anton's proposed patch: > https://lkml.org/lkml/2011/7/24/151 > adding case for 32-bit ppc. > > Tested on the system that first generated the panic and then again > with latest kernel using a PPC VM. I am not able to test the 64-bit > path - I do not have H/W for it and 64-bit PPC VMs (qemu on Intel) > is horribly slow. > > Signed-off-by: David Ahern > CC: Benjamin Herrenschmidt > CC: Anton Blanchard Hmm, Paul, didn't you fix something like this early on? Anyway, I've no objections since I'm really not familiar enough with the PPC side of things.