linux-kernel - Re: [PATCH] ftrace: Remove possible deadlock between register_kprobe() and ftrace_run_update

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Message-ID: <20190628105232.6arwis5u33li6twr@pathway.suse.cz>
Date:   Fri, 28 Jun 2019 12:52:32 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Miroslav Benes <mbenes@...e.cz>
Cc:     Johannes Erdfelt <johannes@...felt.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Jessica Yu <jeyu@...nel.org>, Jiri Kosina <jikos@...nel.org>,
        mhiramat@...nel.org, Ingo Molnar <mingo@...nel.org>,
        tglx@...utronix.de, torvalds@...ux-foundation.org,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        linux-kernel@...r.kernel.org, live-patching@...r.kernel.org
Subject: Re: [PATCH] ftrace: Remove possible deadlock between
 register_kprobe() and ftrace_run_update_code()

On Fri 2019-06-28 09:32:03, Miroslav Benes wrote:
> On Thu, 27 Jun 2019, Petr Mladek wrote:
> > @@ -2611,12 +2610,10 @@ static void ftrace_run_update_code(int command)
> >  {
> >  	int ret;
> >  
> > -	mutex_lock(&text_mutex);
> > -
> >  	ret = ftrace_arch_code_modify_prepare();
> >  	FTRACE_WARN_ON(ret);
> >  	if (ret)
> > -		goto out_unlock;
> > +		return ret;
> 
> Should be just "return;", because the function is "static void".

Grr, I usually check compiler warnings but I evidently skipped it
in this case :-(

Steven, should I send a fixed/folloup patch or will you just
fix it when pushing?

Best Regards,
Petr