Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Sun, 4 Nov 2018 21:58:20 +0100 (CET)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Nadav Amit <namit@vmware.com>
cc:     Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Jiri Kosina <jkosina@suse.cz>,
        Andy Lutomirski <luto@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Dave Hansen <dave.hansen@intel.com>
Subject: Re: [PATCH v3 1/7] Fix "x86/alternatives: Lockdep-enforce text_mutex
 in text_poke*()"
In-Reply-To: <20181102232946.98461-2-namit@vmware.com>
Message-ID: <alpine.DEB.2.21.1811042153430.10744@nanos.tec.linutronix.de>
References: <20181102232946.98461-1-namit@vmware.com> <20181102232946.98461-2-namit@vmware.com>
User-Agent: Alpine 2.21 (DEB 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, 2 Nov 2018, Nadav Amit wrote:

> text_mutex is expected to be held before text_poke() is called, but we
> cannot add a lockdep assertion since kgdb does not take it, and instead
> *supposedly* ensures the lock is not taken and will not be acquired by
> any other core while text_poke() is running.
> 
> The reason for the "supposedly" comment is that it is not entirely clear
> that this would be the case if gdb_do_roundup is zero.
> 
> Add a comment to clarify this behavior, and restore the assertions as
> they were before the recent commit.

It restores nothing. It just removes the assertion.

> This partially reverts commit 9222f606506c ("x86/alternatives:
> Lockdep-enforce text_mutex in text_poke*()")

That opens up the same can of worms again, which took us a while to close.

Can we please instead split out the text_poke() code into a helper function
and have two callers:

    text_poke() which contains the assert

    text_poke_kgdb() which does not

Thanks,

	tglx