[PATCH] workqueue: replace call_rcu with kfree_rcu

[PATCH] workqueue: replace call_rcu with kfree_rcu

[qiang.zhang]

From: Zqiang <qiang.zhang@windriver.com>

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

Signed-off-by: Zqiang <qiang.zhang@windriver.com>
---
 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

Re: [PATCH] workqueue: replace call_rcu with kfree_rcu

[Tejun Heo]

On Wed, Oct 14, 2020 at 04:31:45PM +0800, qiang.zhang@windriver.com 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

[PATCH] workqueue: replace call_rcu with kfree_rcu

[Zqiang]

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

Signed-off-by: Zqiang <qiang.zhang@windriver.com>
---
 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