From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756364Ab3GVOVi (ORCPT ); Mon, 22 Jul 2013 10:21:38 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:31121 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756182Ab3GVOV0 (ORCPT ); Mon, 22 Jul 2013 10:21:26 -0400 X-Authority-Analysis: v=2.0 cv=aqMw+FlV c=1 sm=0 a=Sro2XwOs0tJUSHxCKfOySw==:17 a=Drc5e87SC40A:10 a=Ciwy3NGCPMMA:10 a=eFrZKNUgOFAA:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=Lhi7sDArL4UA:10 a=20KFwNOVAAAA:8 a=VwQbUJbxAAAA:8 a=JfrnYn6hAAAA:8 a=S09kYNnEGi_uWo6_rOcA:9 a=jEp0ucaQiEUA:10 a=3Rfx1nUSh_UA:10 a=jeBq3FmKZ4MA:10 a=Sro2XwOs0tJUSHxCKfOySw==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 67.255.60.225 Message-Id: <20130722142124.870071281@goodmis.org> User-Agent: quilt/0.60-1 Date: Mon, 22 Jul 2013 10:19:52 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Linus Torvalds , Ingo Molnar , Andrew Morton , Masami Hiramatsu , Oleg Nesterov , Peter Zijlstra Subject: [PATCH 05/14] tracing/syscall: Avoid perf_trace_buf_*() if sys_data->perf_events is empty References: <20130722141947.972915744@goodmis.org> Content-Disposition: inline; filename=0005-tracing-syscall-Avoid-perf_trace_buf_-if-sys_data-pe.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleg Nesterov 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. Link: http://lkml.kernel.org/r/20130617170207.GA19806@redhat.com Acked-by: Peter Zijlstra Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt --- kernel/trace/trace_syscalls.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c index 0611562..ac00857 100644 --- a/kernel/trace/trace_syscalls.c +++ b/kernel/trace/trace_syscalls.c @@ -566,6 +566,10 @@ 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)); @@ -583,8 +587,6 @@ 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); } @@ -642,6 +644,10 @@ 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); @@ -661,8 +667,6 @@ 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); } -- 1.7.10.4