Re: [PATCH for-next v5 10/12] rdma_rxe: Fix pool related bugs

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Sep 18, 2020 at 04:15:15PM -0500, Bob Pearson wrote:
> This patch does following:
>   - Replace the rwlock used for pool->pool_lock by a spinlock.
>     Rwlock is a multi-reader single writer lock but there are
>     cases where a multi-writer lock is required, especially where
>     multiple objects can be created at the same time.

Not sure what a multi-write lock is, sounds scary

>   - Be more careful about type checking in pool APIs.
>     Originally each object used in rxe had a pool_entry struct as
>     the first member of it's struct. Since then about half have
>     it first and the other half have it later in the struct. The
>     pool APIs used void * as a hack to avoid type checking. This
>     patch changes the APIs so the pool_entry struct is position
>     independent. When used a parameter a macro is used to convert
>     the object pointer to the entry pointer. The offset of the entry
>     is stored for each pool and used to convert the entry address to
>     the object address.
>   - Provide locked and unlocked versions of the APIs.
>     The current code uses a lock in each API to allow atomic
>     updates to the pools. But some uses fail to work because they
>     combined multiple pool operations and expect them to be
>     atomic. As an example doing a lookup to see if a matching object
>     exists for a multicast group followed by a create of a new group
>     if it does not. By letting the caller take the pool lock and then
>     combine unlocked operations this problem is fixed.
>   - Replace calls to pool APIs with the typesafe versions.
>   - Replaced a few calls to pr_warn with pr_err_once.

This probably needs to be split up

Jason