From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932834AbcDSUaP (ORCPT ); Tue, 19 Apr 2016 16:30:15 -0400 Received: from mail.efficios.com ([78.47.125.74]:55966 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932085AbcDSUaN (ORCPT ); Tue, 19 Apr 2016 16:30:13 -0400 Date: Tue, 19 Apr 2016 20:30:07 +0000 (UTC) From: Mathieu Desnoyers To: rostedt Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , "H. Peter Anvin" , Thomas Gleixner , Jiri Olsa , Masami Hiramatsu , Namhyung Kim , linux-trace-users@vger.kernel.org Message-ID: <1646895533.63372.1461097807190.JavaMail.zimbra@efficios.com> In-Reply-To: <20160419131307.6e32f9f0@gandalf.local.home> References: <20160419143421.829909157@goodmis.org> <20160419143725.473997738@goodmis.org> <1887707510.62932.1461084911586.JavaMail.zimbra@efficios.com> <20160419131307.6e32f9f0@gandalf.local.home> Subject: Re: [RFC][PATCH 3/4] tracing: Add infrastructure to allow set_event_pid to follow children MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [78.47.125.74] X-Mailer: Zimbra 8.6.0_GA_1178 (ZimbraWebClient - FF45 (Linux)/8.6.0_GA_1178) Thread-Topic: tracing: Add infrastructure to allow set_event_pid to follow children Thread-Index: BsXwXbNM0jHKG8lnz9m8E5Vm9ZgaUQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- On Apr 19, 2016, at 1:13 PM, rostedt rostedt@goodmis.org wrote: > On Tue, 19 Apr 2016 16:55:11 +0000 (UTC) > Mathieu Desnoyers wrote: > >> ----- On Apr 19, 2016, at 10:34 AM, rostedt rostedt@goodmis.org wrote: >> >> > From: Steven Rostedt >> > >> > Add the infrastructure needed to have the PIDs in set_event_pid to >> > automatically add PIDs of the children of the tasks that have their PIDs in >> > set_event_pid. This will also remove PIDs from set_event_pid when a task >> > exits >> > >> > This is implemented by adding hooks into the fork and exit tracepoints. On >> > fork, the PIDs are added to the list, and on exit, they are removed. >> > >> > Add a new option called event_fork that when set, PIDs in set_event_pid will >> > automatically get their children PIDs added when they fork, as well as any >> > task that exits will have its PID removed from set_event_pid. >> >> Just out of curiosity: how does it deal with multi-process and multi-thread ? >> What events are expected in each case ? >> > > Not sure what you mean by that. This is in-kernel, and it's simply > tasks. That is, any task (process or thread) that creates another task > has its kernel pid checked. That would be the thread ID as well. So it > works the same with processes as with threads because within the kernel > they are just all just "tasks". You register on sched_process_fork and sched_process_exit tracepoints for adding/removing PIDs to/from your "PID tracker". sched_process_fork() is called both when a process and when a thread is created. sched_process_exit() is called from do_exit(). Ah! and it seems do_exit is called whenever a user-space thread exits. The process exiting system call is rather exit_group(2). I was concerned that you might miss the thread exiting system calls, but it seems OK after digging back into that part of the kernel source code. It's been a while since last time I had to do modeling of the kernel state based on events by myself, sorry about the confusion. :-) Thanks, Mathieu > > -- Steve -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com