[PATCH v5 08/34] cxlflash: Fix to avoid CXL services during EEH

[Tomas Henzl]

On 1.10.2015 17:55, Matthew R. Ochs wrote:
> During an EEH freeze event, certain CXL services should not be
> called until after the hardware reset has taken place. Doing so
> can result in unnecessary failures and possibly cause other ill
> effects by triggering hardware accesses. This translates to a
> requirement to quiesce all threads that may potentially use CXL
> runtime service during this window. In particular, multiple ioctls
> make use of the CXL services when acting on contexts on behalf of
> the user. Thus, it is essential to 'drain' running ioctls _before_
> proceeding with handling the EEH freeze event.
>
> Create the ability to drain ioctls by wrapping the ioctl handler
> call in a read semaphore and then implementing a small routine that
> obtains the write semaphore, effectively creating a wait point for
> all currently executing ioctls.
>
> Signed-off-by: Matthew R. Ochs <mrochs at linux.vnet.ibm.com>
> Signed-off-by: Manoj N. Kumar <manoj at linux.vnet.ibm.com>
> Reviewed-by: Brian King <brking at linux.vnet.ibm.com>
> Reviewed-by: Daniel Axtens <dja at axtens.net>

Reviewed-by: Tomas Henzl <thenzl at redhat.com>

Tomas