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

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Message-ID: <CAFNHFT8pPGGhkX8RR5TJDRZNOC8U7eud7ytErAhNJi0ugmUj+A@mail.gmail.com>
Date:	Sun, 29 May 2016 21:16:26 +0530
From:	Bhaktipriya Shridhar <bhaktipriya96@...il.com>
To:	Oded Gabbay <oded.gabbay@...il.com>
Cc:	Tejun Heo <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()

Thanks Oded. Sending v3 right away :)

On Sun, May 29, 2016 at 8:31 PM, Oded Gabbay <oded.gabbay@...il.com> wrote:
> 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
>>