From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755494Ab3LJP5I (ORCPT ); Tue, 10 Dec 2013 10:57:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:9436 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751687Ab3LJP5E (ORCPT ); Tue, 10 Dec 2013 10:57:04 -0500 Date: Tue, 10 Dec 2013 16:57:44 +0100 From: Oleg Nesterov To: Masami Hiramatsu 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 Message-ID: <20131210155744.GA21466@redhat.com> References: <1386570005-3368-1-git-send-email-namhyung@kernel.org> <1386570005-3368-17-git-send-email-namhyung@kernel.org> <52A6EFD7.8050602@hitachi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52A6EFD7.8050602@hitachi.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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). 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. For example, on ppc it can be always NULL because ppc likely emulates the probed insn. Or did you mean that if get_utask() fails we should report this somehow? Well, GFP_KERNEL should "never" fail and even if it fails we will restart the same insn and retry the allocation. Or did I miss your point completely ? Oleg.