From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757468AbZHZOKy (ORCPT ); Wed, 26 Aug 2009 10:10:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757411AbZHZOKx (ORCPT ); Wed, 26 Aug 2009 10:10:53 -0400 Received: from mtagate4.de.ibm.com ([195.212.17.164]:49356 "EHLO mtagate4.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757449AbZHZOKw (ORCPT ); Wed, 26 Aug 2009 10:10:52 -0400 Date: Wed, 26 Aug 2009 16:10:52 +0200 From: Heiko Carstens To: Frederic Weisbecker Cc: Hendrik Brueckner , Jason Baron , linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, rostedt@goodmis.org, peterz@infradead.org, mathieu.desnoyers@polymtl.ca, jiayingz@google.com, mbligh@google.com, lizf@cn.fujitsu.com, Martin Schwidefsky Subject: Re: [PATCH 08/12] add trace events for each syscall entry/exit Message-ID: <20090826141052.GB5946@osiris.boeblingen.de.ibm.com> References: <20090825141547.GE6114@nowhere> <20090825160237.GG4639@cetus.boeblingen.de.ibm.com> <20090826123550.GD6009@nowhere> <20090826125943.GA5946@osiris.boeblingen.de.ibm.com> <20090826133019.GE6009@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090826133019.GE6009@nowhere> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 26, 2009 at 03:30:22PM +0200, Frederic Weisbecker wrote: > On Wed, Aug 26, 2009 at 02:59:43PM +0200, Heiko Carstens wrote: > > > Yeah, and as told before, syscalls tracing from kernel thread is > > > an interesting point but we can't do it that way. > > > > > > I'm queuing this patch for .32, but I need you Signed-off-by to apply it :) > > > > That won't always work as pointed out in the other example: > > - Process doing sys_init_module then scheduled away > > - User enables syscall tracing -> TIF_SYSCALL_FTRACE gets set > > - init function of the module gets called and is doing kernel_thread() > > (old API) -> kernel thread inherits TIF_SYSCALL_FTRACE. > > > > I don't think that's what you want. You might want to clear the flag for > > new processes during fork (only for kernel threads I would guess). > > > > At least the current patch leaves a hole. > > Ah, there are callsites that use kernel_thread() directly? > Does it means that t->mm could be non NULL for such resulting > kernel threads, in that case it would be hard to hook on > do_fork() to check that. Oh yes, you are right. kernel threads created with kernel_thread() have t->mm != NULL if the forking process has an mm too. There are very few callsites left which still use kernel_thread(). (the last one in s390 driver code will be gone after the next merge window). As far as I can there are only four callsites left (excluding staging): jffs2 and three in net/bluetooth/*