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From: Steven Rostedt <rostedt@goodmis.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Johannes Erdfelt <johannes@erdfelt.com>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Jessica Yu <jeyu@kernel.org>, Jiri Kosina <jikos@kernel.org>,
	Miroslav Benes <mbenes@suse.cz>, Ingo Molnar <mingo@redhat.com>,
	live-patching@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Oops caused by race between livepatch and ftrace
Date: Tue, 21 May 2019 10:42:04 -0400	[thread overview]
Message-ID: <20190521104204.47d4e175@gandalf.local.home> (raw)
In-Reply-To: <20190521141629.bmk5onsaab26qoaw@treble>

On Tue, 21 May 2019 09:16:29 -0500
Josh Poimboeuf <jpoimboe@redhat.com> wrote:

> > Hmm, this may blow up with lockdep, as I believe we already have a
> > locking dependency of:
> > 
> >  text_mutex -> ftrace_lock
> > 
> > And this will reverses it. (kprobes appears to take the locks in this
> > order).
> > 
> > Perhaps have live kernel patching grab ftrace_lock?  
> 
> Where does kprobes call into ftrace with the text_mutex?  I couldn't
> find it.

Hmm, maybe it doesn't. I was looking at the arm_kprobe_ftrace() but
it doesn't call it with text_mutex().

Maybe it is fine, but we had better perform a lot of testing with
lockdep on to make sure.

-- Steve

  reply	other threads:[~2019-05-21 14:42 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-20 19:49 Oops caused by race between livepatch and ftrace Johannes Erdfelt
2019-05-20 20:46 ` Joe Lawrence
2019-05-20 21:09   ` Johannes Erdfelt
2019-05-20 21:19     ` Josh Poimboeuf
2019-05-20 21:39       ` Steven Rostedt
2019-05-21 14:16         ` Josh Poimboeuf
2019-05-21 14:42           ` Steven Rostedt [this message]
2019-05-21 16:42             ` Josh Poimboeuf
2019-05-21 16:53               ` Steven Rostedt
2019-05-29 11:17                 ` Jiri Kosina
2019-05-29 12:06                   ` Steven Rostedt
2019-05-29 12:30                     ` Josh Poimboeuf
2019-05-22 13:00               ` Josh Poimboeuf
2019-05-29 17:29               ` Jessica Yu
2019-05-29 17:39                 ` Josh Poimboeuf
2019-05-29 18:34                   ` Jessica Yu
2019-05-20 21:48       ` Johannes Erdfelt
2019-05-20 21:19     ` Joe Lawrence
2019-05-21 19:27       ` Joe Lawrence
2019-05-21 21:00         ` Josh Poimboeuf

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