Re: [PATCH for-next V7 6/6] IB/ucma: HW Device hot-removal support

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Tue, Aug 04, 2015 at 05:03:28PM +0300, Yishai Hadas wrote:
> Currently, IB/cma remove_one flow blocks until all user descriptor managed by
> IB/ucma are released. This prevents hot-removal of IB devices. This patch
> allows IB/cma to remove devices regardless of user space activity. Upon getting
> the RDMA_CM_EVENT_DEVICE_REMOVAL event we close all the underlying HW resources
> for the given ucontext. The ucontext itself is still alive till its explicit
> destroying by its creator.
> 
> Running applications at that time will have some zombie device, further
> operations may fail.

I've never made it far enough to look at this patch before... It is
Sean's stuff so he is best qualified to comment on it. The rest of the
series is OK now Sean.

> +static void ucma_close_id(struct work_struct *work)
> +{
> +	struct ucma_context *ctx =  container_of(work, struct ucma_context, close_work);
> +
> +	/* Fence to ensure that ctx->closing was seen by all
> +	 * ucma_get_ctx running
> +	 */
> +	mutex_lock(&mut);
> +	mutex_unlock(&mut);

Uh, no. That isn't how to use mutex's.

I don't really see any consistent locking scheme for closing..

Jason
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