Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755842Ab0HaVME (ORCPT ); Tue, 31 Aug 2010 17:12:04 -0400 Received: from hera.kernel.org ([140.211.167.34]:50981 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754045Ab0HaVMC (ORCPT ); Tue, 31 Aug 2010 17:12:02 -0400 Date: Tue, 31 Aug 2010 21:11:42 GMT From: tip-bot for Li Zefan Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, rostedt@goodmis.org, lizf@cn.fujitsu.com, tglx@linutronix.de Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, lizf@cn.fujitsu.com, rostedt@goodmis.org, tglx@linutronix.de In-Reply-To: <4C723644.4040708@cn.fujitsu.com> References: <4C723644.4040708@cn.fujitsu.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/urgent] tracing: Fix a race in function profile Message-ID: Git-Commit-ID: 3aaba20f26f58843e8f20611e5c0b1c06954310f X-Mailer: tip-git-log-daemon 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]); Tue, 31 Aug 2010 21:11:42 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2572 Lines: 82 Commit-ID: 3aaba20f26f58843e8f20611e5c0b1c06954310f Gitweb: http://git.kernel.org/tip/3aaba20f26f58843e8f20611e5c0b1c06954310f Author: Li Zefan AuthorDate: Mon, 23 Aug 2010 16:50:12 +0800 Committer: Steven Rostedt CommitDate: Tue, 31 Aug 2010 16:46:23 -0400 tracing: Fix a race in function profile 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 Cc: stable@kernel.org LKML-Reference: <4C723644.4040708@cn.fujitsu.com> Signed-off-by: Steven Rostedt --- 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 0d88ce9..7cb1f45 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -381,12 +381,19 @@ 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; unsigned long long stddev; #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); @@ -408,7 +415,6 @@ static int function_stat_show(struct seq_file *m, void *v) do_div(stddev, (rec->counter - 1) * 1000); } - mutex_lock(&mutex); trace_seq_init(&s); trace_print_graph_duration(rec->time, &s); trace_seq_puts(&s, " "); @@ -416,11 +422,12 @@ static int function_stat_show(struct seq_file *m, void *v) trace_seq_puts(&s, " "); trace_print_graph_duration(stddev, &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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/