From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753183Ab3FQRHT (ORCPT ); Mon, 17 Jun 2013 13:07:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:12381 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752709Ab3FQRHP (ORCPT ); Mon, 17 Jun 2013 13:07:15 -0400 Date: Mon, 17 Jun 2013 19:02:07 +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 2/3] tracing/syscall: Avoid perf_trace_buf_*() if sys_data->perf_events is empty Message-ID: <20130617170207.GA19806@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_syscall_enter/exit() to check sys_data->{enter,exit}_event->perf_events beforehand. Signed-off-by: Oleg Nesterov --- kernel/trace/trace_syscalls.c | 12 ++++++++---- 1 files changed, 8 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c index 8f2ac73..4d1bd5d 100644 --- a/kernel/trace/trace_syscalls.c +++ b/kernel/trace/trace_syscalls.c @@ -553,6 +553,10 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id) if (!sys_data) return; + head = this_cpu_ptr(sys_data->enter_event->perf_events); + if (hlist_empty(head)) + return; + /* get the size after alignment with the u32 buffer size field */ size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec); size = ALIGN(size + sizeof(u32), sizeof(u64)); @@ -570,8 +574,6 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id) rec->nr = syscall_nr; syscall_get_arguments(current, regs, 0, sys_data->nb_args, (unsigned long *)&rec->args); - - head = this_cpu_ptr(sys_data->enter_event->perf_events); perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL); } @@ -629,6 +631,10 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret) if (!sys_data) return; + head = this_cpu_ptr(sys_data->exit_event->perf_events); + if (hlist_empty(head)) + return; + /* We can probably do that at build time */ size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64)); size -= sizeof(u32); @@ -648,8 +654,6 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret) rec->nr = syscall_nr; rec->ret = syscall_get_return_value(current, regs); - - head = this_cpu_ptr(sys_data->exit_event->perf_events); perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL); } -- 1.5.5.1