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

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Message-ID: <20190628133702.16a54ccf@gandalf.local.home>
Date:   Fri, 28 Jun 2019 13:37:02 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Petr Mladek <pmladek@...e.com>,
        Miroslav Benes <mbenes@...e.cz>, Jessica Yu <jeyu@...nel.org>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        linux-kernel@...r.kernel.org, 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: Remove possible deadlock between
 register_kprobe() and ftrace_run_update_code()

On Fri, 28 Jun 2019 19:33:30 +0200 (CEST)
Jiri Kosina <jikos@...nel.org> wrote:

> On Thu, 27 Jun 2019, Josh Poimboeuf wrote:
> 
> > > How is that supposed to work?
> > > 
> > >     ftrace  	     	
> > > 	prepare()
> > > 	 setrw()
> > > 			setro()
> > > 	patch <- FAIL  
> > 
> > /me dodges frozen shark
> > 
> > You are right of course.  My brain has apparently already shut off for
> > the day.
> > 
> > Maybe a comment or two would help though.  
> 
> I'd actually prefer (perhaps in parallel to the comment) using the 
> __acquires() and __releases() anotations, so that sparse and friends don't 
> get confused by that either.
> 

Care to send a patch? :-)

-- Steve