[PATCH] android: binder: Remove deprecated create_singlethread_workqueue

[PATCH] android: binder: Remove deprecated create_singlethread_workqueue

[Bhaktipriya Shridhar]

The workqueue is being used to run deferred work for the android binder.

The "binder_deferred_workqueue" queues only a single work item and hence
does not require ordering. Also, this workqueue is not being used on a
memory recliam path. Hence, the singlethreaded workqueue has been
replaced with the use of system_wq.

System workqueues have been able to handle high level of concurrency
for a long time now and hence it's not required to have a singlethreaded
workqueue just to gain concurrency. Unlike a dedicated per-cpu workqueue
created with create_singlethread_workqueue(), system_wq allows multiple
work items to overlap executions even on the same CPU; however, a
per-cpu workqueue doesn't have any CPU locality or global ordering
guarantee unless the target CPU is explicitly specified and thus the
increase of local concurrency shouldn't make any difference.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
---
 drivers/android/binder.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 16288e7..562af94 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -59,7 +59,6 @@ static struct dentry *binder_debugfs_dir_entry_proc;
 static struct binder_node *binder_context_mgr_node;
 static kuid_t binder_context_mgr_uid = INVALID_UID;
 static int binder_last_id;
-static struct workqueue_struct *binder_deferred_workqueue;

 #define BINDER_DEBUG_ENTRY(name) \
 static int binder_##name##_open(struct inode *inode, struct file *file) \
@@ -3227,7 +3226,7 @@ binder_defer_work(struct binder_proc *proc, enum binder_deferred_state defer)
 	if (hlist_unhashed(&proc->deferred_work_node)) {
 		hlist_add_head(&proc->deferred_work_node,
 				&binder_deferred_list);
-		queue_work(binder_deferred_workqueue, &binder_deferred_work);
+		schedule_work(&binder_deferred_work);
 	}
 	mutex_unlock(&binder_deferred_lock);
 }
@@ -3679,10 +3678,6 @@ static int __init binder_init(void)
 {
 	int ret;

-	binder_deferred_workqueue = create_singlethread_workqueue("binder");
-	if (!binder_deferred_workqueue)
-		return -ENOMEM;
-
 	binder_debugfs_dir_entry_root = debugfs_create_dir("binder", NULL);
 	if (binder_debugfs_dir_entry_root)
 		binder_debugfs_dir_entry_proc = debugfs_create_dir("proc",
--
2.1.4

Re: [PATCH] android: binder: Remove deprecated create_singlethread_workqueue

[Tejun Heo]

On Sat, Aug 13, 2016 at 10:16:24PM +0530, Bhaktipriya Shridhar wrote:
> The workqueue is being used to run deferred work for the android binder.
> 
> The "binder_deferred_workqueue" queues only a single work item and hence
> does not require ordering. Also, this workqueue is not being used on a
> memory recliam path. Hence, the singlethreaded workqueue has been
> replaced with the use of system_wq.
> 
> System workqueues have been able to handle high level of concurrency
> for a long time now and hence it's not required to have a singlethreaded
> workqueue just to gain concurrency. Unlike a dedicated per-cpu workqueue
> created with create_singlethread_workqueue(), system_wq allows multiple
> work items to overlap executions even on the same CPU; however, a
> per-cpu workqueue doesn't have any CPU locality or global ordering
> guarantee unless the target CPU is explicitly specified and thus the
> increase of local concurrency shouldn't make any difference.
> 
> Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun