From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751395Ab3LKBnp (ORCPT ); Tue, 10 Dec 2013 20:43:45 -0500 Received: from mail9.hitachi.co.jp ([133.145.228.44]:34793 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750902Ab3LKBnm (ORCPT ); Tue, 10 Dec 2013 20:43:42 -0500 Message-ID: <52A7C347.1060402@hitachi.com> Date: Wed, 11 Dec 2013 10:43:35 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.2; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Oleg Nesterov Cc: Namhyung Kim , Steven Rostedt , Srikar Dronamraju , Hyeoncheol Lee , "zhangwei(Jovi)" , Arnaldo Carvalho de Melo , Hemant Kumar , LKML , Namhyung Kim Subject: Re: [PATCH 16/17] uprobes: Allocate ->utask before handler_chain() for tracing handlers References: <1386570005-3368-1-git-send-email-namhyung@kernel.org> <1386570005-3368-17-git-send-email-namhyung@kernel.org> <52A6EFD7.8050602@hitachi.com> <20131210155744.GA21466@redhat.com> In-Reply-To: <20131210155744.GA21466@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2013/12/11 0:57), Oleg Nesterov wrote: > On 12/10, Masami Hiramatsu wrote: >> >> (2013/12/09 15:20), Namhyung Kim wrote: >>> From: Oleg Nesterov >>> >>> uprobe_trace_print() and uprobe_perf_print() need to pass the additional >>> info to call_fetch() methods, currently there is no simple way to do this. >>> >>> current->utask looks like a natural place to hold this info, but we need >>> to allocate it before handler_chain(). >>> >>> This is a bit unfortunate, perhaps we will find a better solution later, >>> but this is simnple and should work right now. >> >> Hmm, when this will happen? > > Perhaps never. Perhaps it will stay forever and we remove get_utask() from > pre_ssout() (it is not needed after this patch). Ah, OK, get_utask() is almost same as kzalloc(). > However I still think we can cleanup this. And to remind, we need to clean > the usage of utask->vaddr in trace_uprobe.c anyway. We can either try to > find another place to pass the info, or we can create a helper(s) for the > tracing handlers to access (and populate if NULL) utask->handler_data. > Note that this (probably) also makes sense because we can unexport > "struct uprobe_task" (but this needs a couple of off-topic cleanups). > > We will see. Lets do the minimal change which can work right now, Namhyung > has enough more serious problems ;) > >> and isn't it better to increment >> miss-hit counter of the uprobe? > > What do you mean? This is not miss-hit and ->utask == NULL is quite normal. But it could skip the handler_chain silently. It could confuse users why their probe doesn't hit as expected. > For example, on ppc it can be always NULL because ppc likely emulates the > probed insn. Hmm, in that case, should uprobes handlers never be called on ppc with this change? > Or did you mean that if get_utask() fails we should report this somehow? I meant that if the uprobes hits some error and not work as expected, it should be reported somehow to users, and miss-hit counter will be a possible option. Thank you, -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com