From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755073AbZANDFu (ORCPT ); Tue, 13 Jan 2009 22:05:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751900AbZANDFl (ORCPT ); Tue, 13 Jan 2009 22:05:41 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:63251 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751653AbZANDFk (ORCPT ); Tue, 13 Jan 2009 22:05:40 -0500 Message-ID: <496D5667.9060301@cn.fujitsu.com> Date: Wed, 14 Jan 2009 11:05:11 +0800 From: Lai Jiangshan User-Agent: Thunderbird 2.0.0.19 (Windows/20081209) MIME-Version: 1.0 To: Steven Rostedt , Ingo Molnar , Linux Kernel Mailing List Subject: Re: [PATCH] ring_buffer: reset write when reserve buffer fail References: <496AB3AA.4060005@cn.fujitsu.com> In-Reply-To: <496AB3AA.4060005@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Steven Rostedt, Have you seen these two patches? (other patch is "[PATCH -tip] ftrace: fix trace_output") Thanks, Lai Lai Jiangshan wrote: > Impact: reset struct buffer_page.write when interrupt storm > > if struct buffer_page.write is not reset, any succedent committing > will corrupted ring_buffer: > > static inline void > rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) > { > ...... > cpu_buffer->commit_page->commit = > cpu_buffer->commit_page->write; > ...... > } > > > when "if (RB_WARN_ON(cpu_buffer, next_page == reader_page))", ring_buffer > is disabled, but some reserved buffers may haven't been committed. > we need reset struct buffer_page.write. > > when "if (unlikely(next_page == cpu_buffer->commit_page))", ring_buffer > is still available, we should not corrupt it. > > Signed-off-by: Lai Jiangshan > --- > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index 8b0daf0..18bfd76 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -1025,12 +1025,8 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, > } > > if (next_page == head_page) { > - if (!(buffer->flags & RB_FL_OVERWRITE)) { > - /* reset write */ > - if (tail <= BUF_PAGE_SIZE) > - local_set(&tail_page->write, tail); > + if (!(buffer->flags & RB_FL_OVERWRITE)) > goto out_unlock; > - } > > /* tail_page has not moved yet? */ > if (tail_page == cpu_buffer->tail_page) { > @@ -1105,6 +1101,10 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, > return event; > > out_unlock: > + /* reset write */ > + if (tail <= BUF_PAGE_SIZE) > + local_set(&tail_page->write, tail); > + > __raw_spin_unlock(&cpu_buffer->lock); > local_irq_restore(flags); > return NULL; > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > > >