From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752110Ab3FQRG3 (ORCPT ); Mon, 17 Jun 2013 13:06:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:61992 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751216Ab3FQRG2 (ORCPT ); Mon, 17 Jun 2013 13:06:28 -0400 Date: Mon, 17 Jun 2013 19:02:04 +0200 From: Oleg Nesterov To: Masami Hiramatsu , Steven Rostedt Cc: Frederic Weisbecker , Ingo Molnar , Srikar Dronamraju , "zhangwei(Jovi)" , linux-kernel@vger.kernel.org Subject: [PATCH 1/3] tracing/function: Avoid perf_trace_buf_*() if event_function.perf_events is empty Message-ID: <20130617170204.GA19803@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130617170142.GA19780@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org perf_trace_buf_prepare() + perf_trace_buf_submit(head, task => NULL) make no sense if hlist_empty(head). Change perf_ftrace_function_call() to check event_function.perf_events beforehand. Signed-off-by: Oleg Nesterov --- kernel/trace/trace_event_perf.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c index 84b1e04..12df557 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -266,6 +266,10 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, struct pt_regs regs; int rctx; + head = this_cpu_ptr(event_function.perf_events); + if (hlist_empty(head)) + return; + #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \ sizeof(u64)) - sizeof(u32)) @@ -279,8 +283,6 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, entry->ip = ip; entry->parent_ip = parent_ip; - - head = this_cpu_ptr(event_function.perf_events); perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0, 1, ®s, head, NULL); -- 1.5.5.1