2020-10-14 14:24:42

by Zhang, Qiang

Subject: [PATCH] workqueue: replace call_rcu with kfree_rcu

From: Zqiang <[email protected]>

The pwq's rcu callback func only to release 'pwq' resources,
can use 'kfree_rcu' instead of 'call_rcu' func.

Signed-off-by: Zqiang <[email protected]>
---
kernel/workqueue.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index ac088ce6059b..8d4fe649631a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3653,11 +3653,6 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
return NULL;
}

-static void rcu_free_pwq(struct rcu_head *rcu)
-{
- kmem_cache_free(pwq_cache,
- container_of(rcu, struct pool_workqueue, rcu));
-}

/*
* Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
@@ -3683,7 +3678,7 @@ static void pwq_unbound_release_workfn(struct work_struct *work)
put_unbound_pool(pool);
mutex_unlock(&wq_pool_mutex);

- call_rcu(&pwq->rcu, rcu_free_pwq);
+ kfree_rcu(pwq, rcu);

/*
* If we're the last pwq going away, @wq is already dead and no one
--
2.17.1

2020-10-26 14:16:41

by Tejun Heo

Subject: Re: [PATCH] workqueue: replace call_rcu with kfree_rcu

On Wed, Oct 14, 2020 at 04:31:45PM +0800, [email protected] wrote:
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index ac088ce6059b..8d4fe649631a 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -3653,11 +3653,6 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
> return NULL;
> }
>
> -static void rcu_free_pwq(struct rcu_head *rcu)
> -{
> - kmem_cache_free(pwq_cache,
> - container_of(rcu, struct pool_workqueue, rcu));
> -}
>
> /*
> * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
> @@ -3683,7 +3678,7 @@ static void pwq_unbound_release_workfn(struct work_struct *work)
> put_unbound_pool(pool);
> mutex_unlock(&wq_pool_mutex);
>
> - call_rcu(&pwq->rcu, rcu_free_pwq);
> + kfree_rcu(pwq, rcu);

kfree_rcu() eventually calls kfree() which is different from
kmem_cache_free(). It can only be used for kmalloc'd areas, not
kmem_cache_alloc'd ones.

Thanks.

--
tejun