linux-kernel - Re: [PATCH] ftrace/x86: Add a comment to why we take text_mutex in ftrace_arch_code_modify

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Message-ID: <20190627213756.25e7b914@gandalf.local.home>
Date:   Thu, 27 Jun 2019 21:37:56 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Petr Mladek <pmladek@...e.com>,
        Miroslav Benes <mbenes@...e.cz>, Jessica Yu <jeyu@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        live-patching@...r.kernel.org,
        Johannes Erdfelt <johannes@...felt.com>,
        Ingo Molnar <mingo@...nel.org>, mhiramat@...nel.org,
        torvalds@...ux-foundation.org
Subject: Re: [PATCH] ftrace/x86: Add a comment to why we take text_mutex in
 ftrace_arch_code_modify_prepare()

On Thu, 27 Jun 2019 20:21:09 -0500
Josh Poimboeuf <jpoimboe@...hat.com> wrote:

> On Thu, Jun 27, 2019 at 09:18:19PM -0400, Steven Rostedt wrote:
> > 
> > From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> > 
> > Taking the text_mutex in ftrace_arch_code_modify_prepare() is to fix a
> > race against module loading and live kernel patching that might try to
> > change the text permissions while ftrace has it as read/write. This
> > really needs to be documented in the code. Add a comment that does such.
> > 
> > Suggested-by: Josh Poimboeuf <jpoimboe@...hat.com>
> > Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

 
> 
> Reviewed-by: Josh Poimboeuf <jpoimboe@...hat.com>
> 

Thanks!

-- Steve