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Date:	Sun, 17 Jul 2016 19:05:40 +0530
From:	Bhaktipriya Shridhar <bhaktipriya96@...il.com>
To:	Leon Romanovsky <leonro@...lanox.com>
Cc:	Matan Barak <matanb@...lanox.com>, netdev@...r.kernel.org,
	linux-rdma@...r.kernel.org,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH] net/mlx5_core/health: Remove deprecated create_singlethread_workqueue

Sure. Will make the changes in v2.

Thanks,
Bhaktipriya


On Sun, Jul 17, 2016 at 10:43 AM, Leon Romanovsky <leonro@...lanox.com> wrote:
> On Sat, Jul 16, 2016 at 01:29:20PM +0530, Bhaktipriya Shridhar wrote:
>> The workqueue health->wq was used as per device private health thread.
>> This was done so that system error handling could be processed
>> concurrently.
>
> Not exactly, AFAIK it was intended to perform delayed work and not
> relevant to concurrency.
>
>> The workqueue has a single workitem(&health->work) and
>> hence doesn't require ordering. It is involved in handling the health of
>> the deviceand is not being used on a memory reclaim path.
>> Hence, the singlethreaded workqueue has been replaced with the use of
>> system_wq.
>
> Yes
>
>>
>> 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.
>
> Not relevant.
>
>>
>> Work item has been flushed in mlx5_health_cleanup() to ensure that
>> there are no pending tasks while disconnecting the driver.
>>
>> Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@...il.com>
>> ---
>>  drivers/net/ethernet/mellanox/mlx5/core/health.c | 7 ++-----
>>  1 file changed, 2 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/health.c b/drivers/net/ethernet/mellanox/mlx5/core/health.c
>> index 42d16b9..9acbccf 100644
>> --- a/drivers/net/ethernet/mellanox/mlx5/core/health.c
>> +++ b/drivers/net/ethernet/mellanox/mlx5/core/health.c
>> @@ -267,7 +267,7 @@ static void poll_health(unsigned long data)
>>       if (in_fatal(dev) && !health->sick) {
>>               health->sick = true;
>>               print_health_info(dev);
>> -             queue_work(health->wq, &health->work);
>> +             schedule_work(&health->work);
>>       }
>>  }
>>
>> @@ -296,7 +296,7 @@ void mlx5_health_cleanup(struct mlx5_core_dev *dev)
>>  {
>>       struct mlx5_core_health *health = &dev->priv.health;
>>
>> -     destroy_workqueue(health->wq);
>> +     flush_work(&health->work);
>>  }
>>
>>  int mlx5_health_init(struct mlx5_core_dev *dev)
>> @@ -311,10 +311,7 @@ int mlx5_health_init(struct mlx5_core_dev *dev)
>>
>>       strcpy(name, "mlx5_health");
>>       strcat(name, dev_name(&dev->pdev->dev));
>> -     health->wq = create_singlethread_workqueue(name);
>>       kfree(name);
>
> You need to remove "name" initialization/usage too.
> It is not needed.
>
>> -     if (!health->wq)
>> -             return -ENOMEM;
>>
>>       INIT_WORK(&health->work, health_care);
>>
>> --
>> 2.1.4
>>
>> --
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