From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=/BZh=RY=vger.kernel.org=linux-kernel-owner@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
X-Spam-Level: 
X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no
	version=3.4.0
Received: from mail.kernel.org (mail.kernel.org [198.145.29.99])
	by smtp.lore.kernel.org (Postfix) with ESMTP id 0B60CC43381
	for <linux-kernel@archiver.kernel.org>; Thu, 21 Mar 2019 18:55:58 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
	by mail.kernel.org (Postfix) with ESMTP id DD96620643
	for <linux-kernel@archiver.kernel.org>; Thu, 21 Mar 2019 18:55:57 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1728992AbfCUSz4 (ORCPT
        <rfc822;linux-kernel@archiver.kernel.org>);
        Thu, 21 Mar 2019 14:55:56 -0400
Received: from mail.kernel.org ([198.145.29.99]:47424 "EHLO mail.kernel.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1728795AbfCUSzy (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 21 Mar 2019 14:55:54 -0400
Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225])
        (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
        (No client certificate requested)
        by mail.kernel.org (Postfix) with ESMTPSA id A7518205F4;
        Thu, 21 Mar 2019 18:55:52 +0000 (UTC)
Date:   Thu, 21 Mar 2019 14:55:51 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Andy Lutomirski <luto@amacapital.net>,
        Juergen Gross <jgross@suse.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
        Joel Fernandes <joel@joelfernandes.org>,
        He Zhe <zhe.he@windriver.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Clark Williams <williams@redhat.com>
Subject: Re: [RFC][PATCH] tracing/x86: Save CR2 before tracing irqsoff on
 error_entry
Message-ID: <20190321145551.4c80c3a7@gandalf.local.home>
In-Reply-To: <20190321182830.GV5996@hirez.programming.kicks-ass.net>
References: <20190320221534.165ab87b@oasis.local.home>
        <20190321083317.GL6058@hirez.programming.kicks-ass.net>
        <20190321090241.GL6521@hirez.programming.kicks-ass.net>
        <20190321104517.GM6521@hirez.programming.kicks-ass.net>
        <20190321093242.4a948198@gandalf.local.home>
        <20190321172203.GS5996@hirez.programming.kicks-ass.net>
        <CALCETrXqmjJt7azNoEtxs2eBkDd-vjUAYvrjNh_RD30DAvksBw@mail.gmail.com>
        <20190321141020.641e313f@gandalf.local.home>
        <20190321182830.GV5996@hirez.programming.kicks-ass.net>
X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, 21 Mar 2019 19:28:30 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

> On Thu, Mar 21, 2019 at 02:10:20PM -0400, Steven Rostedt wrote:
> > On Thu, 21 Mar 2019 11:05:06 -0700
> > Andy Lutomirski <luto@amacapital.net> wrote:
> >   
> > > In the long run, I think the right solution is to rewrite even more of
> > > this mess in C.  We really ought to be able to put the IRQ flag
> > > tracing and the context tracking into C code.  
> > 
> > And once we do that, we can work on getting the irq tracing
> > incorporated into a jump_label type that we could possibly enable
> > lockdep at start up, and then disable it later, even on production
> > systems! That is, to be able to turn it off and bring the system back
> > up to full speed.  
> 
> You forget the stupid amount of data bloat that lockdep brings.

No I didn't. Some users only care about performance, but find memory
cheap.

-- Steve