From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758156Ab0KROF3 (ORCPT ); Thu, 18 Nov 2010 09:05:29 -0500 Received: from hera.kernel.org ([140.211.167.34]:53418 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756877Ab0KROF0 (ORCPT ); Thu, 18 Nov 2010 09:05:26 -0500 Date: Thu, 18 Nov 2010 14:05:04 GMT From: tip-bot for Steven Rostedt Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, eric.dumazet@gmail.com, rostedt@goodmis.org, srostedt@redhat.com, tglx@linutronix.de, jolsa@redhat.com Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, eric.dumazet@gmail.com, rostedt@goodmis.org, srostedt@redhat.com, tglx@linutronix.de, jolsa@redhat.com In-Reply-To: <1289390172-9730-3-git-send-email-jolsa@redhat.com> References: <1289390172-9730-3-git-send-email-jolsa@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] tracing: Fix recursive user stack trace Message-ID: Git-Commit-ID: 91e86e560d0b3ce4c5fc64fd2bbb99f856a30a4e X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Thu, 18 Nov 2010 14:05:04 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 91e86e560d0b3ce4c5fc64fd2bbb99f856a30a4e Gitweb: http://git.kernel.org/tip/91e86e560d0b3ce4c5fc64fd2bbb99f856a30a4e Author: Steven Rostedt AuthorDate: Wed, 10 Nov 2010 12:56:12 +0100 Committer: Steven Rostedt CommitDate: Fri, 12 Nov 2010 21:20:08 -0500 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 --- 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..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