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

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Date:   Fri, 28 Jun 2019 12:54:14 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Johannes Erdfelt <johannes@...felt.com>,
        Jessica Yu <jeyu@...nel.org>, Jiri Kosina <jikos@...nel.org>,
        mhiramat@...nel.org, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        torvalds@...ux-foundation.org,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>, live-patching@...r.kernel.org
Subject: Re: [PATCH] ftrace/x86: Add a comment to why we take text_mutex in
 ftrace_arch_code_modify_prepare()

On Thu 2019-06-27 21:18:19, 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: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr