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[PATCH] gpu: drm: amd: amdkfd: Remove create_workqueue()

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  [PATCH] gpu: drm: amd: amdkfd: Remove create_workqueue() Bhaktipriya Shridhar <bhaktipriya96@gmail.com> - 2016-05-26 20:50 +0200
    Re: [PATCH] gpu: drm: amd: amdkfd: Remove create_workqueue() Tejun Heo <tj@kernel.org> - 2016-05-26 21:00 +0200

#1407667 — [PATCH] gpu: drm: amd: amdkfd: Remove create_workqueue()

alloc_workqueue replaces deprecated create_workqueue().

kfd_process_wq is used for delay destruction. A work item embedded in
kfd_process gets queued to kfd_process_wq and when it executes it
destroys and frees the containing kfd_process and thus itself.

This requires a dedicated workqueue because a work item once queued, may
get freed at any point of time and any external entity cannot
flush the work item. So, in order to wait for such a work item,
it needs to be put on a dedicated workqueue.

kfd_module_exit() calls kfd_process_destroy_wq which ensures that all
pending work items are finished before the module is removed.

flush_workqueue is unnecessary since destroy_workqueue() itself calls
drain_workqueue() which flushes repeatedly till the workqueue becomes empty.

Hence flush_workqueue has been removed.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_process.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index ac00579..b21d3fc8 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -63,13 +63,12 @@ static struct kfd_process *create_process(const struct task_struct *thread);
 void kfd_process_create_wq(void)
 {
 	if (!kfd_process_wq)
-		kfd_process_wq = create_workqueue("kfd_process_wq");
+		kfd_process_wq = alloc_workqueue("kfd_process_wq",0,0);
 }

 void kfd_process_destroy_wq(void)
 {
 	if (kfd_process_wq) {
-		flush_workqueue(kfd_process_wq);
 		destroy_workqueue(kfd_process_wq);
 		kfd_process_wq = NULL;
 	}
--
2.1.4

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#1407675

On Fri, May 27, 2016 at 12:15:17AM +0530, Bhaktipriya Shridhar wrote:
> alloc_workqueue replaces deprecated create_workqueue().
> 
> kfd_process_wq is used for delay destruction. A work item embedded in
> kfd_process gets queued to kfd_process_wq and when it executes it
> destroys and frees the containing kfd_process and thus itself.
> 
> This requires a dedicated workqueue because a work item once queued, may
> get freed at any point of time and any external entity cannot
> flush the work item. So, in order to wait for such a work item,
> it needs to be put on a dedicated workqueue.
> 
> kfd_module_exit() calls kfd_process_destroy_wq which ensures that all
> pending work items are finished before the module is removed.
> 
> flush_workqueue is unnecessary since destroy_workqueue() itself calls
> drain_workqueue() which flushes repeatedly till the workqueue becomes empty.
> 
> Hence flush_workqueue has been removed.

create_workqueue(NAME) maps to alloc_workqueue(NAME, WQ_MEM_RECLAIM, 1),
so the change is effectively dropping WQ_MEM_RECLAIM and changing
concurrency value from 1 to WQ_DFL_ACTIVE.  It'd be nice to explain
why these changes are safe and I think they're. It just needs
explanations.

> Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>

Other than that, Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

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