linux-kernel - RE: [PATCH] IB/core: Make ib_mad_client

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Date:   Wed, 18 Apr 2018 18:51:29 +0000
From:   "Weiny, Ira" <ira.weiny@...el.com>
To:     Håkon Bugge <Haakon.Bugge@...cle.com>,
        Doug Ledford <dledford@...hat.com>,
        "Hiatt, Don" <don.hiatt@...el.com>,
        "Dasaratharaman Chandramouli" <dasaratharaman.chandramouli@...el.com>,
        "Hefty, Sean" <sean.hefty@...el.com>
CC:     "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] IB/core: Make ib_mad_client_id atomic

> 
> Two kernel threads may get the same value for agent.hi_tid, if the agents are
> registered for different ports. As of now, this works, as the agent list is per port.
> 
> It is however confusing and not future robust. Hence, making it atomic.
> 
> Signed-off-by: Håkon Bugge <haakon.bugge@...cle.com>
> Reviewed-by: Jack Morgenstein <jackm@....mellanox.co.il>

Reviewed-by: Ira Weiny <ira.weiny@...el.com>

> ---
>  drivers/infiniband/core/mad.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/infiniband/core/mad.c b/drivers/infiniband/core/mad.c index
> c50596f7f98a..b28452a55a08 100644
> --- a/drivers/infiniband/core/mad.c
> +++ b/drivers/infiniband/core/mad.c
> @@ -59,7 +59,7 @@ module_param_named(recv_queue_size, mad_recvq_size,
> int, 0444);  MODULE_PARM_DESC(recv_queue_size, "Size of receive queue in
> number of work requests");
> 
>  static struct list_head ib_mad_port_list;
> -static u32 ib_mad_client_id = 0;
> +static atomic_t ib_mad_client_id = ATOMIC_INIT(0);
> 
>  /* Port list lock */
>  static DEFINE_SPINLOCK(ib_mad_port_list_lock);
> @@ -377,7 +377,7 @@ struct ib_mad_agent *ib_register_mad_agent(struct
> ib_device *device,
>  	}
> 
>  	spin_lock_irqsave(&port_priv->reg_lock, flags);
> -	mad_agent_priv->agent.hi_tid = ++ib_mad_client_id;
> +	mad_agent_priv->agent.hi_tid =
> atomic_inc_return(&ib_mad_client_id);
> 
>  	/*
>  	 * Make sure MAD registration (if supplied)
> --
> 2.13.6