From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753637Ab1ABIDt (ORCPT ); Sun, 2 Jan 2011 03:03:49 -0500 Received: from mail.windriver.com ([147.11.1.11]:34698 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752866Ab1ABHWW (ORCPT ); Sun, 2 Jan 2011 02:22:22 -0500 From: Paul Gortmaker To: stable@kernel.org, linux-kernel@vger.kernel.org Cc: stable-review@kernel.org, Li Zefan , Steven Rostedt , Paul Gortmaker Subject: [34-longterm 062/260] tracing: Fix a race in function profile Date: Sun, 2 Jan 2011 02:15:58 -0500 Message-Id: <1293952756-15010-63-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.7.3.3 In-Reply-To: <1293952756-15010-1-git-send-email-paul.gortmaker@windriver.com> References: <1293952756-15010-1-git-send-email-paul.gortmaker@windriver.com> X-OriginalArrivalTime: 02 Jan 2011 07:21:13.0445 (UTC) FILETIME=[A305A150:01CBAA4D] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Li Zefan commit 3aaba20f26f58843e8f20611e5c0b1c06954310f upstream. While we are reading trace_stat/functionX and someone just disabled function_profile at that time, we can trigger this: divide error: 0000 [#1] PREEMPT SMP ... EIP is at function_stat_show+0x90/0x230 ... This fix just takes the ftrace_profile_lock and checks if rec->counter is 0. If it's 0, we know the profile buffer has been reset. Signed-off-by: Li Zefan LKML-Reference: <4C723644.4040708@cn.fujitsu.com> Signed-off-by: Steven Rostedt Signed-off-by: Paul Gortmaker --- kernel/trace/ftrace.c | 15 +++++++++++---- 1 files changed, 11 insertions(+), 4 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 2404b59..ed676ba 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -380,11 +380,18 @@ static int function_stat_show(struct seq_file *m, void *v) { struct ftrace_profile *rec = v; char str[KSYM_SYMBOL_LEN]; + int ret = 0; #ifdef CONFIG_FUNCTION_GRAPH_TRACER - static DEFINE_MUTEX(mutex); static struct trace_seq s; unsigned long long avg; #endif + mutex_lock(&ftrace_profile_lock); + + /* we raced with function_profile_reset() */ + if (unlikely(rec->counter == 0)) { + ret = -EBUSY; + goto out; + } kallsyms_lookup(rec->ip, NULL, NULL, NULL, str); seq_printf(m, " %-30.30s %10lu", str, rec->counter); @@ -394,17 +401,17 @@ static int function_stat_show(struct seq_file *m, void *v) avg = rec->time; do_div(avg, rec->counter); - mutex_lock(&mutex); trace_seq_init(&s); trace_print_graph_duration(rec->time, &s); trace_seq_puts(&s, " "); trace_print_graph_duration(avg, &s); trace_print_seq(m, &s); - mutex_unlock(&mutex); #endif seq_putc(m, '\n'); +out: + mutex_unlock(&ftrace_profile_lock); - return 0; + return ret; } static void ftrace_profile_reset(struct ftrace_profile_stat *stat) -- 1.7.3.3