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From: Thomas Gleixner <tglx@linutronix.de>
To: paulmck@kernel.org, "Joel Fernandes \(Google\)" <joel@joelfernandes.org>
Cc: linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	frextrite@gmail.com, Ingo Molnar <mingo@redhat.com>,
	Josh Triplett <josh@joshtriplett.org>,
	kernel-team@android.com, Lai Jiangshan <jiangshanlai@gmail.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	peterz@infradead.org, Petr Mladek <pmladek@suse.com>,
	rcu@vger.kernel.org, rostedt@goodmis.org,
Subject: Re: [PATCH v3 0/5] RCU dyntick nesting counter cleanups for rcu -dev
Date: Sun, 17 May 2020 12:26:43 +0200
Message-ID: <87wo5adfh8.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20200516171223.GC2639@paulmck-ThinkPad-P72>


"Paul E. McKenney" <paulmck@kernel.org> writes:
> And I have allegedly resolved the conflicts with Thomas's and Peter's
> series, or at least the noinstr-rcu-nmi-2020-05-15 branch of that series.
> At least one conflict was completely invisible to "git rebase" (but
> fortunately blindingly obvious to the compiler).  This naturally makes
> me suspect that additional adjustments might be needed.  Especially
> given that misplaced instrumentation_begin() and instrumentation_end()
> calls are invisible not only to the compiler, but also to rcutorture in
> my setup.  (For example, tracing before instrumentation_begin() or after
> instrumentation_end() is a bug.)

there is tooling to verify that. If you merge

  git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git entry-v7-full

into your dev branch (trivial conflict) and after building it, run:

 objtool check -fal $BUILDIR/vmlinux.o

Note: This only covers built-in code. So if you have code you want to
check make sure it's not built as module.

Just did that and it complains about:

../build/vmlinux.o: warning: objtool: rcu_eqs_enter.constprop.0()+0xa9: call to rcu_preempt_deferred_qs() leaves .noinstr.text section

But that's even the case on my branch without your changes.

The call to rcu_preempt_deferred_qs() is definitely before
instrumentation_end() so this needs to be investigated on the objtool
side. Peter?



  reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-04 12:05 Joel Fernandes (Google)
2020-05-04 12:05 ` [PATCH v3 1/5] Revert b8c17e6664c4 ("rcu: Maintain special bits at bottom of ->dynticks counter") Joel Fernandes (Google)
2020-05-04 12:05 ` [PATCH v3 2/5] rcu/tree: Add better tracing for dyntick-idle Joel Fernandes (Google)
2020-05-04 12:05 ` [PATCH v3 3/5] rcu/tree: Clean up dynticks counter usage Joel Fernandes (Google)
2020-05-04 12:05 ` [PATCH v3 4/5] rcu/tree: Remove dynticks_nmi_nesting counter Joel Fernandes (Google)
2020-05-04 12:05 ` [PATCH v3 5/5] trace: events: rcu: Change description of rcu_dyntick trace event Joel Fernandes (Google)
2020-05-04 17:15 ` [PATCH v3 0/5] RCU dyntick nesting counter cleanups for rcu -dev Paul E. McKenney
2020-05-04 17:37   ` Joel Fernandes
2020-05-04 17:44   ` Paul E. McKenney
2020-05-04 18:18     ` Joel Fernandes
2020-05-16 17:12     ` Paul E. McKenney
2020-05-17 10:26       ` Thomas Gleixner [this message]
2020-05-17 16:15         ` Paul E. McKenney
2020-05-17 19:06           ` Thomas Gleixner

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