From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753732Ab2AaKju (ORCPT ); Tue, 31 Jan 2012 05:39:50 -0500 Received: from mail-wi0-f174.google.com ([209.85.212.174]:53462 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753408Ab2AaKjs (ORCPT ); Tue, 31 Jan 2012 05:39:48 -0500 MIME-Version: 1.0 In-Reply-To: <4F278A78.8080300@gmail.com> References: <1327830093-12130-1-git-send-email-namhyung@gmail.com> <4F263B01.4050103@gmail.com> <20120130170548.GA3355@google.com> <4F278A78.8080300@gmail.com> Date: Tue, 31 Jan 2012 02:39:47 -0800 X-Google-Sender-Auth: XsxnrXnxtmH_XB4Ud2vIeBoCiJE Message-ID: Subject: Re: [PATCH] block: add missing block_bio_complete() tracepoint From: Tejun Heo To: Namhyung Kim Cc: Jens Axboe , linux-kernel@vger.kernel.org, Steven Rostedt , dm-devel@redhat.com Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Mon, Jan 30, 2012 at 10:30 PM, Namhyung Kim wrote: > Right, but the point is it could make a NULL pointer dereference during > evaluation of the argument of the TP AFAICS. I'm not sure about the TP > implementation though, I think I was wrong - T_E_C() cannot protect us from > it because it happens just before jumping to the TP, right? > > So I think we need a conditional jump (with the "likely" annotation) for > this even when the TP is disabled. Hmmm... still not following. Where the said NULL dereference happen? TEC conditional is equivalent to "if (COND) TP;". If you don't use TEC, it'll be "if (COND) if (TP enabled) TP;". With TEC, it will be "if (TP enabled) if (COND) TP;". There's no other difference. Thanks. -- tejun