linux-kernel - Re: [PATCH v2 1/2] rcu: Update documentation of rcu_read

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Message-Id: <20180525141942.GB3803@linux.vnet.ibm.com>
Date:   Fri, 25 May 2018 07:19:42 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Anna-Maria Gleixner <anna-maria@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de,
        bigeasy@...utronix.de, ebiederm@...ssion.com
Subject: Re: [PATCH v2 1/2] rcu: Update documentation of rcu_read_unlock()

On Fri, May 25, 2018 at 11:05:06AM +0200, Anna-Maria Gleixner wrote:
> Since commit b4abf91047cf ("rtmutex: Make wait_lock irq safe") the
> explanation in rcu_read_unlock() documentation about irq unsafe rtmutex
> wait_lock is no longer valid.
> 
> Remove it to prevent kernel developers reading the documentation to rely on
> it.
> 
> Suggested-by: Eric W. Biederman <ebiederm@...ssion.com>
> Signed-off-by: Anna-Maria Gleixner <anna-maria@...utronix.de>

Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

Or let me know if you would like me to carry this patch.  Either way,
just let me know!

							Thanx, Paul

> ---
>  include/linux/rcupdate.h | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 36360d07f25b..64644fda3b22 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -653,9 +653,7 @@ static inline void rcu_read_lock(void)
>   * Unfortunately, this function acquires the scheduler's runqueue and
>   * priority-inheritance spinlocks.  This means that deadlock could result
>   * if the caller of rcu_read_unlock() already holds one of these locks or
> - * any lock that is ever acquired while holding them; or any lock which
> - * can be taken from interrupt context because rcu_boost()->rt_mutex_lock()
> - * does not disable irqs while taking ->wait_lock.
> + * any lock that is ever acquired while holding them.
>   *
>   * That said, RCU readers are never priority boosted unless they were
>   * preempted.  Therefore, one way to avoid deadlock is to make sure
> -- 
> 2.15.1
>