Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755723Ab3FQEdo (ORCPT ); Mon, 17 Jun 2013 00:33:44 -0400 Received: from mail4.hitachi.co.jp ([133.145.228.5]:48403 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750937Ab3FQEdn (ORCPT ); Mon, 17 Jun 2013 00:33:43 -0400 Message-ID: <51BE91A4.6020003@hitachi.com> Date: Mon, 17 Jun 2013 13:33:40 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.2; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Oleg Nesterov Cc: Steven Rostedt , Frederic Weisbecker , Ingo Molnar , Srikar Dronamraju , "zhangwei(Jovi)" , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] tracing/kprobes: Avoid perf_trace_buf_*() if ->perf_events is empty References: <20130616172146.GA8533@redhat.com> In-Reply-To: <20130616172146.GA8533@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2884 Lines: 80 (2013/06/17 2:21), Oleg Nesterov wrote: > 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(). > > Signed-off-by: Oleg Nesterov Looks good :) Thank you! Acked-by: Masami Hiramatsu > --- > kernel/trace/trace_kprobe.c | 12 ++++++++---- > 1 files changed, 8 insertions(+), 4 deletions(-) > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 9f46e98..c0af476 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -1157,6 +1157,10 @@ 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)); > @@ -1172,8 +1176,6 @@ 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); > } > @@ -1189,6 +1191,10 @@ 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)); > @@ -1204,8 +1210,6 @@ 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); > } > -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com -- 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/