linux-kernel - Re: [PATCH v2 0/4] RCU dyntick nesting counter cleanups

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Message-ID: <20200328234306.GC19865@paulmck-ThinkPad-P72>
Date:   Sat, 28 Mar 2020 16:43:06 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
        Frederic Weisbecker <fweisbec@...il.com>, frextrite@...il.com,
        Ingo Molnar <mingo@...hat.com>,
        Josh Triplett <josh@...htriplett.org>, kernel-team@...roid.com,
        Lai Jiangshan <jiangshanlai@...il.com>,
        madhuparnabhowmik04@...il.com,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        peterz@...radead.org, Petr Mladek <pmladek@...e.com>,
        rcu@...r.kernel.org, rostedt@...dmis.org, tglx@...utronix.de,
        vpillai@...italocean.com
Subject: Re: [PATCH v2 0/4] RCU dyntick nesting counter cleanups

On Sat, Mar 28, 2020 at 06:16:59PM -0400, Joel Fernandes (Google) wrote:
> These patches clean up the usage of dynticks nesting counters simplifying the
> code, while preserving the usecases.
> 
> It is a much needed simplification, makes the code less confusing, and prevents
> future bugs such as those that arise from forgetting that the
> dynticks_nmi_nesting counter is not a simple counter and can be "crowbarred" in
> common situations.
> 
> rcutorture testing with all TREE RCU configurations succeed with
> CONFIG_RCU_EQS_DEBUG=y and CONFIG_PROVE_LOCKING=y.

Heh!  We now have a three-way collision between Thomas's and Peter's
series, the RCU Tasks Trace series, and this series.  ;-)

Remind me once v5.7-rc1 comes out and let's see what fits where.

							Thanx, Paul

> v1->v2:
> - Rebase on v5.6-rc6
> 
> Joel Fernandes (Google) (4):
> Revert b8c17e6664c4 ("rcu: Maintain special bits at bottom of
> ->dynticks counter")
> rcu/tree: Add better tracing for dyntick-idle
> rcu/tree: Clean up dynticks counter usage
> rcu/tree: Remove dynticks_nmi_nesting counter
> 
> .../Data-Structures/Data-Structures.rst       |  31 +--
> Documentation/RCU/stallwarn.txt               |   6 +-
> include/linux/rcutiny.h                       |   3 -
> include/trace/events/rcu.h                    |  29 +--
> kernel/rcu/rcu.h                              |   4 -
> kernel/rcu/tree.c                             | 188 +++++++-----------
> kernel/rcu/tree.h                             |   4 +-
> kernel/rcu/tree_stall.h                       |   4 +-
> 8 files changed, 105 insertions(+), 164 deletions(-)
> 
> --
> 2.26.0.rc2.310.g2932bb562d-goog
>