linux-kernel - Re: [PATCH v3 -rcu] workqueue: Convert for_each

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Date:   Fri, 16 Aug 2019 09:45:21 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Corbet <corbet@....net>,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-doc@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>, rcu@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH v3 -rcu] workqueue: Convert for_each_wq to use built-in
 list check

On Thu, Aug 15, 2019 at 10:18:42AM -0400, Joel Fernandes (Google) wrote:
> list_for_each_entry_rcu now has support to check for RCU reader sections
> as well as lock. Just use the support in it, instead of explicitly
> checking in the caller.
> 
> Acked-by: Tejun Heo <tj@...nel.org>
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>

Pulled into -rcu for testing and further review, thank you!

							Thanx, Paul

> ---
> v1->v3: Changed lock_is_held() to lockdep_is_held()
> 
>  kernel/workqueue.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 601d61150b65..e882477ebf6e 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -364,11 +364,6 @@ static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
>  			 !lockdep_is_held(&wq_pool_mutex),		\
>  			 "RCU or wq_pool_mutex should be held")
>  
> -#define assert_rcu_or_wq_mutex(wq)					\
> -	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\
> -			 !lockdep_is_held(&wq->mutex),			\
> -			 "RCU or wq->mutex should be held")
> -
>  #define assert_rcu_or_wq_mutex_or_pool_mutex(wq)			\
>  	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\
>  			 !lockdep_is_held(&wq->mutex) &&		\
> @@ -425,9 +420,8 @@ static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
>   * ignored.
>   */
>  #define for_each_pwq(pwq, wq)						\
> -	list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node)		\
> -		if (({ assert_rcu_or_wq_mutex(wq); false; })) { }	\
> -		else
> +	list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node,		\
> +				 lockdep_is_held(&(wq->mutex)))
>  
>  #ifdef CONFIG_DEBUG_OBJECTS_WORK
>  
> -- 
> 2.23.0.rc1.153.gdeed80330f-goog
>