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

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Date:   Fri, 28 Jun 2019 10:51:27 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Petr Mladek <pmladek@...e.com>, Miroslav Benes <mbenes@...e.cz>,
        Johannes Erdfelt <johannes@...felt.com>,
        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>,
        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, Jun 28, 2019 at 11:46:27AM -0400, Steven Rostedt wrote:
> On Fri, 28 Jun 2019 09:54:24 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> > On Fri, 28 Jun 2019 12:52:32 +0200
> > Petr Mladek <pmladek@...e.com> wrote:
> > 
> > > 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?
> > >   
> > 
> > I'll fix it up.
> 
> Also note, this would have been caught with my test suite, as it checks
> for any new warnings.

Sadly, I noticed this while reviewing the code, but then somehow got
distracted and it vanished.  Another review fail...

-- 
Josh