Re: [PATCH rdma-rc] RDMA/ucma: Do not miss ctx destruction steps in some cases

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Jan 05, 2021 at 01:13:27PM +0200, Leon Romanovsky wrote:
> From: Jason Gunthorpe <jgg@nvidia.com>
> 
> The destruction flow is very complicated here because the cm_id can be
> destroyed from the event handler at any time if the device is
> hot-removed. This leaves behind a partial ctx with no cm_id in the xarray.
> 
> Make everything consistent in this flow in all places:
> 
>  - Return the xarray back to XA_ZERO_ENTRY before beginning any
>    destruction. The thread that reaches this first is responsible to
>    kfree, everyone else does nothing.
> 
>  - Test the xarray during the special hot-removal case to block the
>    queue_work, this has much simpler locking and doesn't require a
>    'destroying'
> 
>  - Fix the ref initialization so that it is only positive if cm_id !=
>    NULL, then rely on that to guide the destruction process in all cases.
> 
> Now the new ucma_destroy_private_ctx() can be called in all places that
> want to free the ctx, including all the error unwinds, and none of the
> details are missed.
> 
> Fixes: a1d33b70dbbc ("RDMA/ucma: Rework how new connections are passed through event delivery")
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> ---
>  drivers/infiniband/core/ucma.c | 135 ++++++++++++++++++---------------
>  1 file changed, 72 insertions(+), 63 deletions(-)

Applied to for-rc, thanks

Jason