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Date:   Fri, 12 Jul 2019 00:49:51 -0400
From:   Joel Fernandes <joel@joelfernandes.org>
To:     linux-kernel@vger.kernel.org
Cc:     Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Bjorn Helgaas <bhelgaas@google.com>,
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        Thomas Gleixner <tglx@linutronix.de>, will@kernel.org,
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Subject: Re: [PATCH v1 1/6] rcu: Add support for consolidated-RCU reader
 checking
Message-ID: <20190712044951.GA92297@google.com>
References: <20190711234401.220336-1-joel@joelfernandes.org>
 <20190711234401.220336-2-joel@joelfernandes.org>
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On Thu, Jul 11, 2019 at 07:43:56PM -0400, Joel Fernandes (Google) wrote:
> This patch adds support for checking RCU reader sections in list
> traversal macros. Optionally, if the list macro is called under SRCU or
> other lock/mutex protection, then appropriate lockdep expressions can be
> passed to make the checks pass.
> 
> Existing list_for_each_entry_rcu() invocations don't need to pass the
> optional fourth argument (cond) unless they are under some non-RCU
> protection and needs to make lockdep check pass.
> 
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> ---
>  include/linux/rculist.h  | 29 ++++++++++++++++++++++++-----
>  include/linux/rcupdate.h |  7 +++++++
>  kernel/rcu/Kconfig.debug | 11 +++++++++++
>  kernel/rcu/update.c      | 26 ++++++++++++++++++++++++++
>  4 files changed, 68 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/rculist.h b/include/linux/rculist.h
> index e91ec9ddcd30..78c15ec6b2c9 100644
> --- a/include/linux/rculist.h
> +++ b/include/linux/rculist.h
> @@ -40,6 +40,23 @@ static inline void INIT_LIST_HEAD_RCU(struct list_head *list)
>   */
>  #define list_next_rcu(list)	(*((struct list_head __rcu **)(&(list)->next)))
>  
> +/*
> + * Check during list traversal that we are within an RCU reader
> + */
> +
> +#define SIXTH_ARG(a1, a2, a3, a4, a5, a6, ...) a6
> +#define COUNT_VARGS(...) SIXTH_ARG(dummy, ## __VA_ARGS__, 4, 3, 2, 1, 0)

Fyi, I made a cosmetic change by deleting the above 2 unused macros.

- Joel