From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932133Ab3GBU0z (ORCPT ); Tue, 2 Jul 2013 16:26:55 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:33065 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755598Ab3GBUY2 (ORCPT ); Tue, 2 Jul 2013 16:24:28 -0400 X-Authority-Analysis: v=2.0 cv=KtrPKBqN c=1 sm=0 a=Sro2XwOs0tJUSHxCKfOySw==:17 a=Drc5e87SC40A:10 a=Ciwy3NGCPMMA:10 a=oHkucnw5I60A:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=Su328q2Qjh8A:10 a=20KFwNOVAAAA:8 a=VwQbUJbxAAAA:8 a=3nbZYyFuAAAA:8 a=wniiS7EUZDIcOveDR-UA:9 a=jEp0ucaQiEUA:10 a=EvKJbDF4Ut8A:10 a=jeBq3FmKZ4MA:10 a=Sro2XwOs0tJUSHxCKfOySw==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 67.255.60.225 Message-Id: <20130702202425.507708254@goodmis.org> User-Agent: quilt/0.60-1 Date: Tue, 02 Jul 2013 16:22:18 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Andrew Morton , Masami Hiramatsu , Oleg Nesterov Subject: [for-next][PATCH 02/14] tracing/kprobes: Avoid perf_trace_buf_*() if ->perf_events is empty References: <20130702202216.623562799@goodmis.org> Content-Disposition: inline; filename=0002-tracing-kprobes-Avoid-perf_trace_buf_-if-perf_events.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() make no sense if this task/CPU has no active counters. Change kprobe_perf_func() and kretprobe_perf_func() to check call->perf_events beforehand and return if this list is empty. For example, "perf record -e some_probe -p1". Only /sbin/init will report, all other threads which hit the same probe will do perf_trace_buf_prepare/perf_trace_buf_submit just to realize that nobody wants perf_swevent_event(). Link: http://lkml.kernel.org/r/20130620173806.GA13151@redhat.com Acked-by: Masami Hiramatsu Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt --- kernel/trace/trace_kprobe.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index f237417..c35bebe 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -1156,6 +1156,10 @@ kprobe_perf_func(struct trace_probe *tp, struct pt_regs *regs) int size, __size, dsize; int rctx; + head = this_cpu_ptr(call->perf_events); + if (hlist_empty(head)) + return; + dsize = __get_data_size(tp, regs); __size = sizeof(*entry) + tp->size + dsize; size = ALIGN(__size + sizeof(u32), sizeof(u64)); @@ -1171,8 +1175,6 @@ kprobe_perf_func(struct trace_probe *tp, struct pt_regs *regs) entry->ip = (unsigned long)tp->rp.kp.addr; memset(&entry[1], 0, dsize); store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize); - - head = this_cpu_ptr(call->perf_events); perf_trace_buf_submit(entry, size, rctx, entry->ip, 1, regs, head, NULL); } @@ -1188,6 +1190,10 @@ kretprobe_perf_func(struct trace_probe *tp, struct kretprobe_instance *ri, int size, __size, dsize; int rctx; + head = this_cpu_ptr(call->perf_events); + if (hlist_empty(head)) + return; + dsize = __get_data_size(tp, regs); __size = sizeof(*entry) + tp->size + dsize; size = ALIGN(__size + sizeof(u32), sizeof(u64)); @@ -1203,8 +1209,6 @@ kretprobe_perf_func(struct trace_probe *tp, struct kretprobe_instance *ri, entry->func = (unsigned long)tp->rp.kp.addr; entry->ret_ip = (unsigned long)ri->ret_addr; store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize); - - head = this_cpu_ptr(call->perf_events); perf_trace_buf_submit(entry, size, rctx, entry->ret_ip, 1, regs, head, NULL); } -- 1.7.10.4