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From: Jason Gunthorpe <jgg@nvidia.com>
To: Anand Khoje <anand.a.khoje@oracle.com>
Cc: linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org,
	dledford@redhat.com, haakon.bugge@oracle.com, leon@kernel.org
Subject: Re: [PATCH v5 for-next 3/3] IB/core: Obtain subnet_prefix from cache in IB devices
Date: Fri, 25 Jun 2021 09:48:12 -0300	[thread overview]
Message-ID: <20210625124812.GS2371267@nvidia.com> (raw)
In-Reply-To: <5fd99709-8a90-e875-1ed2-74f5bcce6eec@oracle.com>

On Fri, Jun 25, 2021 at 11:33:58AM +0530, Anand Khoje wrote:
> 
> If the above change is to be made, there could arise a scenario in which:
>  In case of a cache_update event, another application/module could try to
> call ib_query_port() and read subnet_prefix while the cache is still getting
> updated and the application/module could end up reading a stale value of
> subnet_prefix.

Applications relying on this data must hook the event and update their
state when the event fires.

So long as ib_query_port returns the correct value in the event
handler it is all OK. This whole thing is racy - the HW can change the
subnet_prefix at anytime, this is just shuffling the race around.

> - Is it possible that different GIDs in the gid_table will have different
> values of subnet_prefix?

Valid GIDs should have the same prefix

Jason

  reply	other threads:[~2021-06-25 12:48 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-16 15:45 [PATCH v5 for-next 0/3] IB/core: Obtaining subnet_prefix from cache in Anand Khoje
2021-06-16 15:45 ` [PATCH v5 for-next 1/3] IB/core: Removed port validity check from ib_get_cached_subnet_prefix Anand Khoje
2021-06-16 15:45 ` [PATCH v5 for-next 2/3] IB/core: Shuffle locks in ib_port_data to save memory Anand Khoje
2021-06-16 15:45 ` [PATCH v5 for-next 3/3] IB/core: Obtain subnet_prefix from cache in IB devices Anand Khoje
2021-06-17  6:41   ` Leon Romanovsky
2021-06-21 23:49   ` Jason Gunthorpe
2021-06-23 13:03     ` Anand Khoje
2021-06-24 17:54       ` Jason Gunthorpe
2021-06-25  6:03         ` Anand Khoje
2021-06-25 12:48           ` Jason Gunthorpe [this message]
2021-06-21 23:52 ` [PATCH v5 for-next 0/3] IB/core: Obtaining subnet_prefix from cache in Jason Gunthorpe

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