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From: "Håkon Bugge" <haakon.bugge@oracle.com>
To: jackm <jackm@dev.mellanox.co.il>
Cc: Doug Ledford <dledford@redhat.com>,
	Jason Gunthorpe <jgg@ziepe.ca>, Don Hiatt <don.hiatt@intel.com>,
	Dasaratharaman Chandramouli
	<dasaratharaman.chandramouli@intel.com>,
	Ira Weiny <ira.weiny@intel.com>,
	Sean Hefty <sean.hefty@intel.com>,
	OFED mailing list <linux-rdma@vger.kernel.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] IB/core: Make ib_mad_client_id atomic
Date: Tue, 1 May 2018 08:40:07 +0200	[thread overview]
Message-ID: <451F533C-60E1-4154-9540-92CB83276446@oracle.com> (raw)
In-Reply-To: <20180501073816.00001ec6@dev.mellanox.co.il>



> On 1 May 2018, at 06:38, jackm <jackm@dev.mellanox.co.il> wrote:
> 
> On Mon, 30 Apr 2018 13:10:49 -0400
> Doug Ledford <dledford@redhat.com> wrote:
> 
> Looks good!

Yes, absolutely!

Håkon

> 
> -Jack
> 
>> On Mon, 2018-04-30 at 08:49 -0600, Jason Gunthorpe wrote:
>>> On Mon, Apr 23, 2018 at 10:16:18PM +0300, jackm wrote:
>>> 
>>>>>> TIDs need to be globally unique on the entire machine.    
>>>> Jason, that is not exactly correct.  
>>> 
>>> The expecation for /dev/umad users is that they all receive locally
>>> unique TID prefixes. The kernel may be OK to keep things
>>> port-specific but it is slightly breaking the API we are presenting
>>> to userspace to allow them to alias..
>>> 
>>> Jason  
>> 
>> Would people be happier with this commit message then:
>> 
>> IB/core: Make ib_mad_client_id atomic
>> 
>> Currently, the kernel protects access to the agent ID allocator on a
>> per port basis using a spinlock, so it is impossible for two
>> apps/threads on the same port to get the same TID, but it is entirely
>> possible for two threads on different ports to end up with the same
>> TID.  
>> 
>> As this can be confusing (regardless of it being legal according to
>> the IB Spec 1.3, C13-18.1.1, in section 13.4.6.4 - TransactionID
>> usage), and as the rdma-core user space API for /dev/umad devices
>> implies unique TIDs even across ports, make the TID an atomic type so
>> that no two allocations, regardless of port number, will be the same.
>> 
>> Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
>> Reviewed-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
>> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
>> Reviewed-by: Zhu Yanjun <yanjun.zhu@oracle.com>
>> Signed-off-by: Doug Ledford <dledford@redhat.com>
>> 
>> 
> 
> --
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      reply	other threads:[~2018-05-01  6:40 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-18 14:24 Håkon Bugge
2018-04-18 18:51 ` Weiny, Ira
2018-04-19  2:59 ` Yanjun Zhu
2018-04-20  3:55 ` Doug Ledford
2018-04-20 15:34   ` Jason Gunthorpe
2018-04-23 14:19     ` Håkon Bugge
2018-04-23 19:16       ` jackm
2018-04-26 16:06         ` Håkon Bugge
2018-04-26 18:32           ` jackm
     [not found]             ` <9fdd3ec4-ee91-5442-e753-25d2ecd27ea9@xsintricity.com>
     [not found]               ` <A58D5192-06E7-46A3-869C-273E9A2BC128@oracle.com>
2018-04-27 19:08                 ` Doug Ledford
2018-04-30 11:50                   ` Håkon Bugge
2018-04-30 14:49         ` Jason Gunthorpe
2018-04-30 17:10           ` Doug Ledford
2018-04-30 17:49             ` Weiny, Ira
2018-04-30 23:01             ` Jason Gunthorpe
2018-05-01  4:38             ` jackm
2018-05-01  6:40               ` Håkon Bugge [this message]

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