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Message-ID: <20190712110142.GS3402@hirez.programming.kicks-ass.net>
Date: Fri, 12 Jul 2019 13:01:42 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc: linux-kernel@...r.kernel.org,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
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Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
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"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
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kernel-hardening@...ts.openwall.com,
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Thomas Gleixner <tglx@...utronix.de>, will@...nel.org,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>
Subject: Re: [PATCH v1 1/6] rcu: Add support for consolidated-RCU reader
checking
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@...lfernandes.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)
You don't seem to actually use it in this patch; also linux/kernel.h has
COUNT_ARGS().
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