From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathieu Desnoyers Subject: Re: [for-next][PATCH 08/20] tracing: Warn if a tracepoint is not set via debugfs Date: Thu, 13 Mar 2014 15:24:46 +0000 (UTC) Message-ID: <970465661.2809.1394724286739.JavaMail.zimbra@efficios.com> References: <20140307150920.881849073@goodmis.org> <285520930.1511.1394642395537.JavaMail.zimbra@efficios.com> <20140312135059.2d497b58@gandalf.local.home> <1906756968.1732.1394650035535.JavaMail.zimbra@efficios.com> <20140312145802.4819511e@gandalf.local.home> <1177120325.1928.1394653861180.JavaMail.zimbra@efficios.com> <20140312204907.6b8d402c@gandalf.local.home> <209084517.2310.1394680253793.JavaMail.zimbra@efficios.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <209084517.2310.1394680253793.JavaMail.zimbra@efficios.com> Sender: linux-kernel-owner@vger.kernel.org To: Steven Rostedt Cc: "Frank Ch. Eigler" , linux-kernel@vger.kernel.org, Ingo Molnar , Frederic Weisbecker , Andrew Morton , Johannes Berg , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Greg Kroah-Hartman , lttng-dev , Rusty Russell , Andi Kleen List-Id: lttng-dev@lists.lttng.org ----- Original Message ----- > From: "Mathieu Desnoyers" > To: "Steven Rostedt" > Cc: "Frank Ch. Eigler" , linux-kernel@vger.kernel.org, "Ingo Molnar" , "Frederic > Weisbecker" , "Andrew Morton" , "Johannes Berg" > , "Linus Torvalds" , "Peter Zijlstra" > , "Thomas Gleixner" , "Greg Kroah-Hartman" , > "lttng-dev" , "Rusty Russell" , "Andi Kleen" > Sent: Wednesday, March 12, 2014 11:10:53 PM > Subject: Re: [for-next][PATCH 08/20] tracing: Warn if a tracepoint is not set via debugfs > > ----- Original Message ----- > > From: "Steven Rostedt" > > To: "Mathieu Desnoyers" > > Cc: "Frank Ch. Eigler" , linux-kernel@vger.kernel.org, > > "Ingo Molnar" , "Frederic > > Weisbecker" , "Andrew Morton" > > , "Johannes Berg" > > , "Linus Torvalds" > > , "Peter Zijlstra" > > , "Thomas Gleixner" , "Greg > > Kroah-Hartman" , > > "lttng-dev" , "Rusty Russell" > > , "Andi Kleen" > > Sent: Wednesday, March 12, 2014 8:49:07 PM > > Subject: Re: [for-next][PATCH 08/20] tracing: Warn if a tracepoint is not > > set via debugfs > > > > On Wed, 12 Mar 2014 19:51:01 +0000 (UTC) > > Mathieu Desnoyers wrote: > > > > > This only leaves tracepoints in header files and the impact of LTO as > > > requirements for having tracepoint callsites with the same name across > > > modules. > > > > The only thing that needs to be unique is the struct tracepoint > > __tracepoint_##name. There should not be any duplicates of those. I > > can't see how the LTO would duplicate a data structure without screwing > > everything (not just tracepoints) up. > > > > We can still have more than one trace_##name() called, as that is > > handled by the static key. > > Hrm, I seem to have mixed up the concerns regarding compiler > optimisations between the static keys with those related to tracepoints > (including that their predecessors "kernel markers" worked more like > static keys than tracepoint). I did work in both area pretty much at the > same time back in 2007-2008. > > Having gotten my head back up straight, I now see the point in your > proposal. Thanks for bearing with me. > > Even if we ever want to have tracepoints within header files, as long > as we have the DECLARE_TRACE() within the header, and a DEFINE_TRACE() > in one location in the loaded kernel image (or a loaded module we depend > on), it should be possible too. All tracepoint.c cares about is the site > defined by DEFINE_TRACE(). I just prepared a patch implementing your idea. I will post it as RFC very soon. The callers will still need to be adapted, so this is just to show the tracepoint.c/h modifications. Thanks! Mathieu > > > > > Note, I'm scrambling to get ready for my trip tomorrow. Thus, I'm not > > as much at the computer. I may work on some patches in my 6 hour > > layover though. > > Allright. Have a good trip! > > Thanks, > > Mathieu > > > > > -- Steve > > > > -- > Mathieu Desnoyers > EfficiOS Inc. > http://www.efficios.com > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com