From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753281Ab0H0NO0 (ORCPT ); Fri, 27 Aug 2010 09:14:26 -0400 Received: from mail.windriver.com ([147.11.1.11]:52343 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753249Ab0H0NOZ (ORCPT ); Fri, 27 Aug 2010 09:14:25 -0400 Message-ID: <4C77BB6B.9090706@windriver.com> Date: Fri, 27 Aug 2010 21:19:39 +0800 From: DDD User-Agent: Thunderbird 2.0.0.24 (X11/20100317) MIME-Version: 1.0 To: Peter Zijlstra , fweisbec@gmail.com CC: mingo@elte.hu, acme@redhat.com, paulus@samba.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] perf: fix possible divide-by-zero in perf_swevent_overflow() References: <1282824438-13970-1-git-send-email-dongdong.deng@windriver.com> <1282824727.1975.747.camel@laptop> <4C765FD3.9060904@windriver.com> <1282827486.1975.845.camel@laptop> <4C77ADC1.5030502@windriver.com> <1282913445.1975.2414.camel@laptop> In-Reply-To: <1282913445.1975.2414.camel@laptop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 27 Aug 2010 13:14:07.0891 (UTC) FILETIME=[BB19AE30:01CB45E9] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra wrote: > On Fri, 2010-08-27 at 20:21 +0800, DDD wrote: > >>>> Maybe the root cause was from kgdb/hw_breakpoint_layer, >>> Yeah, I think there's a bug in the hw_breakpoint stuff, does something >>> like the below fix it? > >> Thanks for your patch, but I still could reproduce the problem with your >> patch. > > Frederic, any clue as to what makes hw breakpoints go funny and have > last_period == 0? Hi Peter, Thanks for you take care of it, I have got the root cause of it now. It is the kgdb using hw_breakpoint_layer's API problem, and I have a RFC patch for it.(maybe it is not correctly), I will contact with Jason to fix this problem. Thank you very much, Dongdong > >>> --- >>> kernel/hw_breakpoint.c | 13 ++++++++++++- >>> 1 files changed, 12 insertions(+), 1 deletions(-) >>> >>> diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c >>> index d71a987..f57ebee 100644 >>> --- a/kernel/hw_breakpoint.c >>> +++ b/kernel/hw_breakpoint.c >>> @@ -600,9 +600,20 @@ static int __init init_hw_breakpoint(void) >>> } >>> core_initcall(init_hw_breakpoint); >>> >>> +static int hw_breakpoint_enable(struct perf_event *event) >>> +{ >>> + struct hw_perf_event *hwc = &event->hw; >>> + >>> + if (hwc->sample_period) { >>> + hwc->last_period = hwc->sample_period; >>> + perf_swevent_set_period(event); >>> + } >>> + >>> + return arch_install_hw_breakpoint(event); >>> +} >>> >>> struct pmu perf_ops_bp = { >>> - .enable = arch_install_hw_breakpoint, >>> + .enable = hw_breakpoint_enable, >>> .disable = arch_uninstall_hw_breakpoint, >>> .read = hw_breakpoint_pmu_read, >>> }; >>> >>> >