Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752506AbcDZAHg (ORCPT ); Mon, 25 Apr 2016 20:07:36 -0400 Received: from mail-pf0-f174.google.com ([209.85.192.174]:34557 "EHLO mail-pf0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752462AbcDZAHc (ORCPT ); Mon, 25 Apr 2016 20:07:32 -0400 Date: Mon, 25 Apr 2016 17:07:26 -0700 From: Alexei Starovoitov To: Arnaldo Carvalho de Melo Cc: David Ahern , Peter Zijlstra , Frederic Weisbecker , Ingo Molnar , Adrian Hunter , Brendan Gregg , Alexander Shishkin , Alexei Starovoitov , He Kuang , Jiri Olsa , Masami Hiramatsu , Milian Wolff , Namhyung Kim , Stephane Eranian , Thomas Gleixner , Vince Weaver , Wang Nan , Zefan Li , Linux Kernel Mailing List Subject: Re: [PATCH/RFC v2] perf core: Allow setting up max frame stack depth via sysctl Message-ID: <20160426000724.GA28705@ast-mbp.thefacebook.com> References: <20160422205232.GB7004@kernel.org> <571AA02B.90107@gmail.com> <20160422221806.GA62857@ast-mbp.thefacebook.com> <20160425161425.GA25218@kernel.org> <20160425162706.GB25218@kernel.org> <20160425192229.GC25218@kernel.org> <20160425200646.GA23875@ast-mbp.thefacebook.com> <20160425201750.GD25218@kernel.org> <20160425215947.GA25915@ast-mbp.thefacebook.com> <20160425234138.GA16708@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160425234138.GA16708@kernel.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 923 Lines: 26 On Mon, Apr 25, 2016 at 08:41:39PM -0300, Arnaldo Carvalho de Melo wrote: > > +int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH; > + > +static inline size_t perf_callchain_entry__sizeof(void) > +{ > + return (sizeof(struct perf_callchain_entry) + > + sizeof(__u64) * sysctl_perf_event_max_stack); > +} > @@ -1144,6 +1144,14 @@ static struct ctl_table kern_table[] = { > .extra1 = &zero, > .extra2 = &one_hundred, > }, > + { > + .procname = "perf_event_max_stack", > + .data = NULL, /* filled in by handler */ > + .maxlen = sizeof(sysctl_perf_event_max_stack), > + .mode = 0644, > + .proc_handler = perf_event_max_stack_handler, > + .extra1 = &zero, > + }, you need to define a max value otherwise perf_callchain_entry__sizeof will overflow. Sure it's root only facility, but still not nice. 1M? Anything above 1M stack frames would be insane anyway. The rest looks good. Thanks!