linux-kernel - Re: [PATCH v2] gpu: drm: amd: amdkfd: Remove create

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Date:	Sun, 29 May 2016 18:01:05 +0300
From:	Oded Gabbay <oded.gabbay@...il.com>
To:	Bhaktipriya Shridhar <bhaktipriya96@...il.com>
Cc:	tj@...nel.org, Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>,
	David Airlie <airlied@...ux.ie>,
	Maling list - DRI developers 
	<dri-devel@...ts.freedesktop.org>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] gpu: drm: amd: amdkfd: Remove create_workqueue()

On Thu, May 26, 2016 at 10:37 PM, Bhaktipriya Shridhar
<bhaktipriya96@...il.com> wrote:
> alloc_workqueue replaces deprecated create_workqueue().
>
> create_workqueue has been replaced with alloc_workqueue with max_active
> as 0 since there is no need for throttling the number of active work items.
>
> WQ_MEM_RECLAIM has not been set to because kfd_process_wq will not be used in
> memory reclaim path.
>
> 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@...il.com>
> ---
>  Changes in v2:
>         - added explanation for setting concurrency value to
>           WQ_DFL_ACTIVE
>         - added explanation for dropping WQ_MEM_RECLAIM
>
>  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);

You are missing a space between the arguments. Seem you forgot to run
checkpatch.pl ;)

Send a new patch and I'll add it to amdkfd's tree.

Thanks,

   Oded

>  }
>
>  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
>