net/mlx5: optimize critical section in device free

  When PMD releases shared IB device context, It locks the
mlx5_ibv_list_mutex lock throughout the function so that it does not
happen while removing a device from the list, another process will try
to insert another device into it.
On the other hand, having removed the device from the list even if it
has not yet released all of its resources, it should not care about
other processes and can release the lock.

However, the PMD does not release the lock even though it can, and
performs a number of operations, some of which include sleep and may be
long.
To improve this, shorten the lock time to the minimum necessary.

Signed-off-by: Michael Baum <michaelba@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>
---
 drivers/net/mlx5/mlx5.c | 2 ++
 1 file changed, 2 insertions(+)
  

Hi,

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Michael Baum
> Sent: Tuesday, July 21, 2020 3:04 PM
> To: dev@dpdk.org
> Cc: Matan Azrad <matan@mellanox.com>; Slava Ovsiienko
> <viacheslavo@mellanox.com>
> Subject: [dpdk-dev] [PATCH] net/mlx5: optimize critical section in device free
> 
> When PMD releases shared IB device context, It locks the
> mlx5_ibv_list_mutex lock throughout the function so that it does not
> happen while removing a device from the list, another process will try
> to insert another device into it.
> On the other hand, having removed the device from the list even if it
> has not yet released all of its resources, it should not care about
> other processes and can release the lock.
> 
> However, the PMD does not release the lock even though it can, and
> performs a number of operations, some of which include sleep and may be
> long.
> To improve this, shorten the lock time to the minimum necessary.
> 
> Signed-off-by: Michael Baum <michaelba@mellanox.com>
> Acked-by: Matan Azrad <matan@mellanox.com>
> ---
>  drivers/net/mlx5/mlx5.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c
> index 846398d..70338e5 100644
> --- a/drivers/net/mlx5/mlx5.c
> +++ b/drivers/net/mlx5/mlx5.c
> @@ -939,6 +939,7 @@ struct mlx5_dev_ctx_shared *
>  	mlx5_mr_release_cache(&sh->share_cache);
>  	/* Remove context from the global device list. */
>  	LIST_REMOVE(sh, next);
> +	pthread_mutex_unlock(&mlx5_dev_ctx_list_mutex);
>  	/*
>  	 *  Ensure there is no async event handler installed.
>  	 *  Only primary process handles async device events.
> @@ -968,6 +969,7 @@ struct mlx5_dev_ctx_shared *
>  		mlx5_flow_id_pool_release(sh->flow_id_pool);
>  	pthread_mutex_destroy(&sh->txpp.mutex);
>  	mlx5_free(sh);
> +	return;
>  exit:
>  	pthread_mutex_unlock(&mlx5_dev_ctx_list_mutex);
>  }
> --
> 1.8.3.1

Patch applied to next-net-mlx,

Kindest regards,
Raslan Darawsheh