Re: [PATCH 2/3] scsi/fcoe: Add a local_lock to fcoe_percpu

[Sebastian Andrzej Siewior]

On 2021-11-16 18:59:55 [-0800], Davidlohr Bueso wrote:
> fcoe_get_paged_crc_eof() relies on the caller having preemption
> disabled to ensure the per-CPU fcoe_percpu context remains valid
> throughout the call. This is done by either holding spinlocks
> (such as bnx2fc_global_lock or qedf_global_lock) or the get_cpu()
> from fcoe_alloc_paged_crc_eof(). This last one breaks PREEMPT_RT
> semantics as there can be memory allocation and end up sleeping
> in atomic contexts.
> 
> Introduce a local_lock_t to struct fcoe_percpu that will keep the
> non-RT case the same, mapping to preempt_disable/enable, while
> RT will use a per-CPU spinlock allowing the region to be preemptible
> but still maintain CPU locality. The other users of fcoe_percpu
> are already safe in this regard and do not require local_lock()ing.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>

Acked-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

Sebastian