From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754275AbYKRPvO (ORCPT ); Tue, 18 Nov 2008 10:51:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752197AbYKRPu6 (ORCPT ); Tue, 18 Nov 2008 10:50:58 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:59196 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752086AbYKRPu5 (ORCPT ); Tue, 18 Nov 2008 10:50:57 -0500 Date: Tue, 18 Nov 2008 16:50:45 +0100 From: Ingo Molnar To: Steven Rostedt Cc: Frederic Weisbecker , Linux Kernel Subject: Re: [PATCH 3/3] tracing/function-return-tracer: add the overrun field Message-ID: <20081118155045.GJ30358@elte.hu> References: <4920D571.4050007@gmail.com> <20081117084923.GD28786@elte.hu> <4921BA25.3090704@gmail.com> <20081118084755.GK17838@elte.hu> <20081118145154.GC30358@elte.hu> <20081118151326.GH30358@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00,DNS_FROM_SECURITYSAGE autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] 0.0 DNS_FROM_SECURITYSAGE RBL: Envelope sender in blackholes.securitysage.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Steven Rostedt wrote: > > On Tue, 18 Nov 2008, Ingo Molnar wrote: > > > > > > > > that reminds me: ti->ret_stack[] should be moved to task->ret_stack[]. > > > > That way we decouple its size from any kernel stack size limits. > > > > (thread-info resides at one end of the kernel stack, on x86) > > > > > > Yeah, I recommended that to Frederic to save space. But that can be > > > dangerous. Using task instead would be safer with the downside of > > > making the task struct even bigger. > > > > We almost never put new stuff into thread_info - we have the > > lockdep lock stack in the task structure too, for similar reasons. > > Yeah, it was just a recommendation, and perhaps not a good one ;-) > > Frederic, it is better if you move the array from the thread info to > the task struct. It will take up more memory but it is a hell of a > lot safer. The pro here definitely outways the con. if the memory footprint starts mattering we could turn this into a single pointer to an array - and add/remove these arrays (from all tasks currently running) as the tracer is turned on/off. Ingo