Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753682Ab0AYWOe (ORCPT ); Mon, 25 Jan 2010 17:14:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753281Ab0AYWOd (ORCPT ); Mon, 25 Jan 2010 17:14:33 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53676 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751628Ab0AYWOc (ORCPT ); Mon, 25 Jan 2010 17:14:32 -0500 Message-ID: <4B5E17B8.4090002@redhat.com> Date: Mon, 25 Jan 2010 17:14:16 -0500 From: Masami Hiramatsu User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.7) Gecko/20100120 Fedora/3.0.1-1.fc11 Thunderbird/3.0.1 MIME-Version: 1.0 To: Frederic Weisbecker CC: Mathieu Desnoyers , Steven Rostedt , Ingo Molnar , LKML , Li Zefan , Lai Jiangshan Subject: Re: [RFC PATCH 03/10] ftrace: Drop the ftrace_profile_enabled checks in tracing hot path References: <1264122982-1553-1-git-send-regression-fweisbec@gmail.com> <1264122982-1553-4-git-send-regression-fweisbec@gmail.com> <1264125917.31321.312.camel@gandalf.stny.rr.com> <20100122022858.GA2604@Krystal> <1264129978.31321.333.camel@gandalf.stny.rr.com> <20100122040959.GA11827@Krystal> <1264135966.31321.375.camel@gandalf.stny.rr.com> <20100122123450.GA19348@Krystal> <20100125205814.GD5087@nowhere> In-Reply-To: <20100125205814.GD5087@nowhere> X-Enigmail-Version: 1.0 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: 2526 Lines: 70 Frederic Weisbecker wrote: > On Fri, Jan 22, 2010 at 07:34:51AM -0500, Mathieu Desnoyers wrote: >> * Steven Rostedt (rostedt@goodmis.org) wrote: >>> On Thu, 2010-01-21 at 23:09 -0500, Mathieu Desnoyers wrote: >>>> * Steven Rostedt (rostedt@goodmis.org) wrote: >>> >>>>> Hmm, interesting. Maybe something like that might work. But what if >>>>> CONFIG_PREEMPT is enabled but CONFIG_FREEZER is not? >>>> >>>> Then you may want to make the function tracer depend on CONFIG_FREEZER, >>>> but maybe Masami has other ideas ? >>> >>> egad no! This is just to help add guarantees to those that use the >>> function tracer that when the tracing is disabled, it is guaranteed that >>> no more tracing will be called by the function tracer. Currently, >>> nothing relies on this. But we may add cases that might need this. >> >> Yep, identifying tracer quiescent state can become handy. >> >>> >>> In fact, only those that need this requirement would need to do this >>> trick. Anyway, we could make those depend on CONFIG_FREEZER, but that >>> just seems to be a strange dependency. >> >> This makes me wonder (question for Masami)... >> >> static int __kprobes check_safety(void) >> { >> int ret = 0; >> #if defined(CONFIG_PREEMPT) && defined(CONFIG_FREEZER) >> ret = freeze_processes(); >> if (ret == 0) { >> struct task_struct *p, *q; >> do_each_thread(p, q) { >> if (p != current && p->state == TASK_RUNNING && >> p->pid != 0) { >> printk("Check failed: %s is running\n",p->comm); >> ret = -1; >> goto loop_end; >> } >> } while_each_thread(p, q); > > > > How does that deal with kernel threads that don't freeze? Hmm, right. It can't handle non-freezable kernel threads. > Also freezing every processes seems a bit of a heavy thing for that. > Looks like a synchronize_tasks() would be really useful. Sure :-) Maybe, I'd better remove booster support on preemptive kernel until then. Thank you, -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America), Inc. Software Solutions Division e-mail: mhiramat@redhat.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/