From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752861Ab0KMC5y (ORCPT ); Fri, 12 Nov 2010 21:57:54 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.124]:46796 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751408Ab0KMC5w (ORCPT ); Fri, 12 Nov 2010 21:57:52 -0500 X-Authority-Analysis: v=1.1 cv=+c36koQ5Dcj/1qolKHjtkYAGXvrVJRRiKMp+84F5sLg= c=1 sm=0 a=7p6bkbCgeYgA:10 a=Q9fys5e9bTEA:10 a=OPBmh+XkhLl+Enan7BmTLg==:17 a=VwQbUJbxAAAA:8 a=20KFwNOVAAAA:8 a=pGLkceISAAAA:8 a=meVymXHHAAAA:8 a=jqXQ-xn1kw274rXKkuYA:9 a=nAUpLxcKp-zlUU9QwrkA:7 a=kmeed5hNP8REOk56bdS7tZT0jnwA:4 a=PUjeQqilurYA:10 a=jEp0ucaQiEUA:10 a=MSl-tDqOz04A:10 a=jeBq3FmKZ4MA:10 a=OPBmh+XkhLl+Enan7BmTLg==:117 X-Cloudmark-Score: 0 X-Originating-IP: 67.242.120.143 Subject: [PATCH][GIT PULL] tracing: Fix recursive user stack trace From: Steven Rostedt To: LKML Cc: Ingo Molnar , Frederic Weisbecker , Andrew Morton , Eric Dumazet , Jiri Olsa Content-Type: text/plain; charset="ISO-8859-15" Date: Fri, 12 Nov 2010 21:57:49 -0500 Message-ID: <1289617069.12418.575.camel@gandalf.stny.rr.com> 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 Ingo, This also includes the two other patches I submitted previously. I just rebased the third patch with Eric's recommendation. Please pull the latest tip/perf/urgent-3 tree, which can be found at: git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git tip/perf/urgent-3 Steven Rostedt (1): tracing: Fix recursive user stack trace ---- kernel/trace/trace.c | 19 +++++++++++++++++++ 1 files changed, 19 insertions(+), 0 deletions(-) --------------------------- commit 91e86e560d0b3ce4c5fc64fd2bbb99f856a30a4e Author: Steven Rostedt Date: Wed Nov 10 12:56:12 2010 +0100 tracing: Fix recursive user stack trace 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 ] [ Eric Dumazet recommended using __this_cpu_* instead of __get_cpu_* ] Cc: Eric Dumazet Signed-off-by: Jiri Olsa LKML-Reference: <1289390172-9730-3-git-send-email-jolsa@redhat.com> Signed-off-by: Steven Rostedt diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 82d9b81..ee6a733 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 (__this_cpu_read(user_stack_count)) + goto out; + + __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); + + __this_cpu_dec(user_stack_count); + + out: + preempt_enable(); } #ifdef UNUSED