Re: [PATCH 6/9] workqueue: Convert for_each_wq to use built-in list check (v2)

From: Paul E. McKenney
Date: Tue Jul 16 2019 - 14:43:50 EST


On Mon, Jul 15, 2019 at 10:37:02AM -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 explictly
> checking in the caller.
>
> Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>

We need an ack from one of the subsystem maintainers on this one.

Thanx, Paul

> ---
> 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, \
> + lock_is_held(&(wq->mutex).dep_map))
>
> #ifdef CONFIG_DEBUG_OBJECTS_WORK
>
> --
> 2.22.0.510.g264f2c817a-goog
>