From: Steven Rostedt <rostedt@goodmis.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Petr Mladek <pmladek@suse.com>, Jessica Yu <jeyu@redhat.com>,
Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is broken in RCU code
Date: Mon, 8 May 2017 17:16:42 -0400 [thread overview]
Message-ID: <20170508171642.7968c110@gandalf.local.home> (raw)
In-Reply-To: <20170508204333.xc3isvr4riv26his@treble>
On Mon, 8 May 2017 15:43:33 -0500
Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> Ok, so just to clarify. Is there a bug in the ftrace stack tracer in
> the following situation?
>
> 1. RCU isn't watching
> 2. An NMI hits
> 3. ist_enter() calls into the ftrace stack tracer, before
> rcu_nmi_enter() is called, so RCU isn't watching yet
No, because in the ftrace stack tracer there's:
if (in_nmi())
return;
At the very beginning.
-- Steve
> 4. The ftrace stack tracer calls rcu_irq_enter(), which has no effect,
> so RCU still isn't watching
> 5. Hilarity ensues in the ftrace stack tracer
>
next prev parent reply other threads:[~2017-05-08 21:16 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-04 10:55 [PATCH 0/3] livepatch/rcu: Handle some subtle issues between livepatching and RCU Petr Mladek
2017-05-04 10:55 ` [PATCH 1/3] livepatch/rcu: Guarantee consistency when patching idle kthreads Petr Mladek
2017-05-04 10:55 ` [PATCH 2/3] livepatch/rcu: Warn when system consistency is broken in RCU code Petr Mladek
2017-05-08 16:51 ` Josh Poimboeuf
2017-05-08 19:13 ` Steven Rostedt
2017-05-08 19:47 ` Josh Poimboeuf
2017-05-08 20:15 ` Paul E. McKenney
2017-05-08 20:43 ` Josh Poimboeuf
2017-05-08 20:51 ` Josh Poimboeuf
2017-05-08 21:08 ` Paul E. McKenney
2017-05-08 21:07 ` Paul E. McKenney
2017-05-08 21:18 ` Steven Rostedt
2017-05-08 21:30 ` Paul E. McKenney
2017-05-08 22:16 ` Josh Poimboeuf
2017-05-08 22:36 ` Paul E. McKenney
2017-05-09 16:18 ` Josh Poimboeuf
2017-05-09 16:36 ` Paul E. McKenney
2017-05-10 16:04 ` Petr Mladek
2017-05-10 16:45 ` Paul E. McKenney
2017-05-10 17:58 ` Josh Poimboeuf
2017-05-11 12:40 ` Miroslav Benes
2017-05-11 15:03 ` Josh Poimboeuf
2017-05-08 21:16 ` Steven Rostedt [this message]
2017-05-08 20:18 ` Steven Rostedt
2017-05-11 12:50 ` Miroslav Benes
2017-05-11 13:52 ` Petr Mladek
2017-05-11 14:50 ` Paul E. McKenney
2017-05-11 15:27 ` Josh Poimboeuf
2017-05-11 12:44 ` Petr Mladek
2017-05-04 10:55 ` [PATCH 3/3] livepatch/rcu: Disable livepatch removal when safety is not guaranteed Petr Mladek
2017-05-04 16:55 ` [PATCH 0/3] livepatch/rcu: Handle some subtle issues between livepatching and RCU Paul E. McKenney
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