From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752166AbZFBSqP (ORCPT ); Tue, 2 Jun 2009 14:46:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751344AbZFBSqB (ORCPT ); Tue, 2 Jun 2009 14:46:01 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.124]:34875 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751225AbZFBSqA (ORCPT ); Tue, 2 Jun 2009 14:46:00 -0400 Message-Id: <20090602184601.361575345@goodmis.org> References: <20090602183036.621443366@goodmis.org> User-Agent: quilt/0.46-1 Date: Tue, 02 Jun 2009 14:30:39 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Frederic Weisbecker , stable@kernel.org, "Luis Claudio R. Goncalves" , Oleg Nesterov Subject: [PATCH 3/3] function-graph: add memory barriers for accessing tasks ret_stack Content-Disposition: inline; filename=0003-function-graph-add-memory-barriers-for-accessing-tas.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt The code that handles the tasks ret_stack allocation for every task assumes that only an interrupt can cause issues (even though interrupts are disabled). In reality, the code is allocating the ret_stack for tasks that may be running on other CPUs and there are not efficient memory barriers to handle this case. [ Impact: prevent crash due to using of uninitialized ret_stack variables ] Signed-off-by: Steven Rostedt --- kernel/trace/ftrace.c | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 20e0660..1664d3f 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -2580,12 +2580,12 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list) } if (t->ret_stack == NULL) { - t->curr_ret_stack = -1; - /* Make sure IRQs see the -1 first: */ - barrier(); - t->ret_stack = ret_stack_list[start++]; atomic_set(&t->tracing_graph_pause, 0); atomic_set(&t->trace_overrun, 0); + t->curr_ret_stack = -1; + /* Make sure the tasks see the -1 first: */ + smp_wmb(); + t->ret_stack = ret_stack_list[start++]; } } while_each_thread(g, t); -- 1.6.3.1 --