linux-kernel - Re: [PATCH v2 1/6] Fix "x86/alternatives: Lockdep-enforce text_mutex in text

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Message-ID: <20180906214122.GG9358@worktop.programming.kicks-ass.net>
Date:   Thu, 6 Sep 2018 23:41:22 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Nadav Amit <namit@...are.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        linux-arch <linux-arch@...r.kernel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Jiri Kosina <jkosina@...e.cz>,
        Andy Lutomirski <luto@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH v2 1/6] Fix "x86/alternatives: Lockdep-enforce text_mutex
 in text_poke*()"

On Thu, Sep 06, 2018 at 08:57:38PM +0000, Nadav Amit wrote:
> at 1:25 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > On Thu, Sep 06, 2018 at 07:58:40PM +0000, Nadav Amit wrote:
> >>> With that CR3 trickery, we can rid ourselves of the text_mutex
> >>> requirement, since concurrent text_poke is 'safe'. That would clean up
> >>> the kgdb code quite a bit.
> >> 
> >> I don’t know. I’m somewhat worried with multiple mechanisms potentially
> >> changing the same code at the same time - and maybe ending up with some
> >> mess.
> > 
> > kgdb only pokes INT3, that should be pretty safe.
> 
> Maybe I misunderstand your point. If you want me to get rid of text_mutex
> completely,

No, just the ugly things kgdb does with it.