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Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is broken in RCU code

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From Steven Rostedt <rostedt@goodmis.org>
Newsgroups linux.kernel
Subject Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is broken in RCU code
Date Mon, 08 May 2017 23:20:02 +0200
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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
>

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[PATCH 0/3] livepatch/rcu: Handle some subtle issues between livepatching and RCU Petr Mladek <pmladek@suse.com> - 2017-05-04 13:00 +0200
  [PATCH 1/3] livepatch/rcu: Guarantee consistency when patching idle kthreads Petr Mladek <pmladek@suse.com> - 2017-05-04 13:00 +0200
  [PATCH 2/3] livepatch/rcu: Warn when system consistency is broken in RCU code Petr Mladek <pmladek@suse.com> - 2017-05-04 13:00 +0200
    Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-08 19:00 +0200
      Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Steven Rostedt <rostedt@goodmis.org> - 2017-05-08 21:20 +0200
        Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-08 21:50 +0200
          Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-08 22:20 +0200
            Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-08 22:50 +0200
              Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-08 23:00 +0200
                Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-08 23:10 +0200
              Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-08 23:10 +0200
                Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Steven Rostedt <rostedt@goodmis.org> - 2017-05-08 23:20 +0200
                Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-08 23:40 +0200
                Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-09 00:20 +0200
                Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-09 00:40 +0200
                Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-09 18:20 +0200
                Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-09 18:40 +0200
                Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Petr Mladek <pmladek@suse.com> - 2017-05-10 18:10 +0200
                Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-10 18:50 +0200
                Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-10 20:00 +0200
                Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is broken  in RCU code Miroslav Benes <mbenes@suse.cz> - 2017-05-11 14:50 +0200
                Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-11 17:10 +0200
              Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Steven Rostedt <rostedt@goodmis.org> - 2017-05-08 23:20 +0200
          Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Steven Rostedt <rostedt@goodmis.org> - 2017-05-08 22:20 +0200
            Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is broken  in RCU code Miroslav Benes <mbenes@suse.cz> - 2017-05-11 15:00 +0200
        Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Petr Mladek <pmladek@suse.com> - 2017-05-11 16:00 +0200
          Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-11 17:00 +0200
          Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-11 17:30 +0200
      Re: [PATCH 2/3] livepatch/rcu: Warn when system consistency is  broken in RCU code Petr Mladek <pmladek@suse.com> - 2017-05-11 14:50 +0200
  Re: [PATCH 0/3] livepatch/rcu: Handle some subtle issues between  livepatching and RCU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-04 19:00 +0200

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