linux-kernel - Re: [PATCH] RDMA/device: Fix a race between mad_client and cm

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Date: Thu, 4 Jan 2024 08:37:28 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Shifeng Li <lishifeng@...gfor.com.cn>
Cc: leon@...nel.org, wenglianfa@...wei.com, gustavoars@...nel.org,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	Shifeng Li <lishifeng1992@....com>,
	"Ding, Hui" <dinghui@...gfor.com.cn>
Subject: Re: [PATCH] RDMA/device: Fix a race between mad_client and cm_client
 init

On Thu, Jan 04, 2024 at 02:48:14PM +0800, Shifeng Li wrote:

> The root cause is that mad_client and cm_client may init concurrently
> when devices_rwsem write semaphore is downgraded in enable_device_and_get() like:

That can't be true, the module loader infrastructue ensures those two
things are sequential.

You are trying to say that the post-client fixup stuff will still see
the DEVICE_REGISTERED before it reaches the clients_rwsem lock?

That probably just says the clients_rwsem should be obtained before
changing the DEVICE_STATE too :\

Jason