From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754667AbbAOWsA (ORCPT ); Thu, 15 Jan 2015 17:48:00 -0500 Received: from ozlabs.org ([103.22.144.67]:60636 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752896AbbAOWr6 (ORCPT ); Thu, 15 Jan 2015 17:47:58 -0500 Message-ID: <1421362067.23332.4.camel@ellerman.id.au> Subject: Re: [PATCH] tracing: Allow raw_syscall tracepoints to work from boot From: Michael Ellerman To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, paulmck@linux.vnet.ibm.com, Andrew Morton , tglx@linutronix.de, mathieu.desnoyers@efficios.com, xiakaixu@huawei.com Date: Fri, 16 Jan 2015 09:47:47 +1100 In-Reply-To: <20150115085817.46708f7f@grimm.local.home> References: <1421188517-18312-1-git-send-email-mpe@ellerman.id.au> <20150114130300.75c5d2ce@gandalf.local.home> <1421302240.11409.6.camel@ellerman.id.au> <20150115085817.46708f7f@grimm.local.home> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.7-0ubuntu1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2015-01-15 at 08:58 -0500, Steven Rostedt wrote: > On Thu, 15 Jan 2015 17:10:40 +1100 > Michael Ellerman wrote: > > > > I like my version better, but your call. > > Of course you do :-) You've got to admit mine is a lot neater looking :) > I thought about it a bit, and both versions are really hacks. But in > the end, I'd rather not touch the swapper task because that might give > us some unwanted side effects. Yeah that's true. I don't *think* there would be, but touching swapper is certainly something one should do with caution. > I don't really like my approach where I need to disable and re-enable > all tracepoints. I was thinking of only enabling and disabling just the > syscall ones, but I could imagine another tracepoint with a reg that > could be affected by early boot as well, so I left it touching all > events. My patch is fine for mainline, but I could make a patch for > 3.20 that will only restart a tracepoint if it has its own reg/unreg > functions and does not use the default ones. > > Your patch fixes syscall events. I wanted something that will fix any > event with its own special registration that might also use > for_each_process_thread() or some other call that does not work before > init is created. Yep, that is definitely a benefit. I don't think there are heaps of folks using tracepoints from boot, so it's possible something else was broken and we haven't noticed yet. cheers