From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
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 09:16:29 -0500 [thread overview]
Message-ID: <20190521141629.bmk5onsaab26qoaw@treble> (raw)
In-Reply-To: <20190520173910.6da9ddaf@gandalf.local.home>
On Mon, May 20, 2019 at 05:39:10PM -0400, Steven Rostedt wrote:
> On Mon, 20 May 2019 16:19:31 -0500
> Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index a12aff849c04..8259d4ba8b00 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -34,6 +34,7 @@
> > #include <linux/hash.h>
> > #include <linux/rcupdate.h>
> > #include <linux/kprobes.h>
> > +#include <linux/memory.h>
> >
> > #include <trace/events/sched.h>
> >
> > @@ -2610,10 +2611,12 @@ static void ftrace_run_update_code(int command)
> > {
> > int ret;
> >
> > + mutex_lock(&text_mutex);
> > +
>
> 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.
--
Josh
next prev parent reply other threads:[~2019-05-21 14:16 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 [this message]
2019-05-21 14:42 ` Steven Rostedt
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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