From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757703Ab0KLPVR (ORCPT ); Fri, 12 Nov 2010 10:21:17 -0500 Received: from mail-ww0-f44.google.com ([74.125.82.44]:60651 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757293Ab0KLPVQ (ORCPT ); Fri, 12 Nov 2010 10:21:16 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=ag2hhhV9jN3/MJF+vH2BHLtmrgfEzoCQaTe8wQLZ2oaEzBJGsM1AJnWVYvKrLjQitB PKISSX0qE7cDFmu3suupe/j4lC8BFnFj/8BVRlHPHbUCBT7GVUN4b3nHMLQDGrssCPzb 8vibA/80KUcC8O+l5TVcNWqHUHnQhfbtSOsHI= Subject: Re: [PATCH 3/3] tracing: Fix recursive user stack trace From: Eric Dumazet To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , Frederic Weisbecker , Jiri Olsa In-Reply-To: <20101112151223.183540991@goodmis.org> References: <20101112151045.672405637@goodmis.org> <20101112151223.183540991@goodmis.org> Content-Type: text/plain; charset="UTF-8" Date: Fri, 12 Nov 2010 16:21:11 +0100 Message-ID: <1289575271.3185.256.camel@edumazet-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le vendredi 12 novembre 2010 à 10:10 -0500, Steven Rostedt a écrit : > pièce jointe document texte brut > (0003-tracing-Fix-recursive-user-stack-trace.patch) > From: Steven Rostedt > > The user stack trace can fault when examining the trace. Which > would call the do_page_fault handler, which would trace again, > which would do the user stack trace, which would fault and call > do_page_fault again ... > > Thus this is causing a recursive bug. We need to have a recursion > detector here. > > [ Resubmitted by Jiri Olsa ] > Signed-off-by: Jiri Olsa > LKML-Reference: <1289390172-9730-3-git-send-email-jolsa@redhat.com> > Signed-off-by: Steven Rostedt > --- > kernel/trace/trace.c | 19 +++++++++++++++++++ > 1 files changed, 19 insertions(+), 0 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 82d9b81..0215e87 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -1284,6 +1284,8 @@ void trace_dump_stack(void) > __ftrace_trace_stack(global_trace.buffer, flags, 3, preempt_count()); > } > > +static DEFINE_PER_CPU(int, user_stack_count); > + > void > ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) > { > @@ -1302,6 +1304,18 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) > if (unlikely(in_nmi())) > return; > > + /* > + * prevent recursion, since the user stack tracing may > + * trigger other kernel events. > + */ > + preempt_disable(); > + if (__get_cpu_var(user_stack_count)) > + goto out; > + if (__this_cpu_read(user_stack_count)) goto out; > + __get_cpu_var(user_stack_count)++; __this_cpu_inc(user_stack_count); > + > + > + > event = trace_buffer_lock_reserve(buffer, TRACE_USER_STACK, > sizeof(*entry), flags, pc); > if (!event) > @@ -1319,6 +1333,11 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) > save_stack_trace_user(&trace); > if (!filter_check_discard(call, entry, buffer, event)) > ring_buffer_unlock_commit(buffer, event); > + > + __get_cpu_var(user_stack_count)--; __this_cpu_dec(user_stack_count); > + > + out: > + preempt_enable(); > } > > #ifdef UNUSED