Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755413Ab3FPR0H (ORCPT ); Sun, 16 Jun 2013 13:26:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41678 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755324Ab3FPR0D (ORCPT ); Sun, 16 Jun 2013 13:26:03 -0400 Date: Sun, 16 Jun 2013 19:21:46 +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/kprobes: Avoid perf_trace_buf_*() if ->perf_events is empty Message-ID: <20130616172146.GA8533@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130616172128.GA8515@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 Content-Length: 2485 Lines: 67 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 --- 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); } -- 1.5.5.1 -- 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/