Re: [PATCH 1/5] scsi: bnx2i: convert to workqueue

[Johannes Thumshirn <jth@kernel.org>]

On 04/10/2017 07:12 PM, Sebastian Andrzej Siewior wrote:
> The driver creates its own per-CPU threads which are updated based on CPU
> hotplug events. It is also possible to use kworkers and remove some of the
> infrastructure get the same job done while saving a few lines of code.
>
> The DECLARE_PER_CPU() definition is moved into the header file where it
> belongs. bnx2i_percpu_io_thread() becomes bnx2i_percpu_io_work() which is
> mostly the same code. The outer loop (kthread_should_stop()) gets removed and
> the remaining code is shifted to the left.
> bnx2i_queue_scsi_cmd_resp() is mostly the same. The code checked ->iothread to
> decide if there is an active per-CPU thread. With the kworkers this is no
> longer possible nor required.
> The allocation of struct bnx2i_work does not happen with ->p_work_lock held
> which is not required. I am unsure about the call-stack so I can't say
> if this qualifies it for the allocation with GFP_KERNEL instead of
> GFP_ATOMIC (it is not _bh lock but as I said, I don't know the context).
> The allocation case has been reversed so the inner if case is called on
> !bnx2i_work and is just the invocation one function since the lock is not
> held during allocation. The init of the new bnx2i_work struct is now
> done also without the ->p_work_lock held: it is a new object, nobody
> knows about it yet. It should be enough to hold the lock while adding
> this item to the list. I am unsure about that atomic_inc() so I keep
> things as they were.
>
> The remaining part is the removal CPU hotplug notifier since it is taken
> care by the workqueue code.
>
> This patch was only compile-tested due to -ENODEV.
>
> Cc: QLogic-Storage-Upstream@qlogic.com
> Cc: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>