On Thu, Jul 29, 2021 at 12:52:15PM +0200, Sebastian Andrzej Siewior wrote:
> Non RT kernels need to protect FPU against preemption and bottom half
> processing. This is achieved by disabling bottom halves via
> local_bh_disable() which implictly disables preemption.
> 
> On RT kernels this protection mechanism is not sufficient because
> local_bh_disable() does not disable preemption. It serializes bottom half
> related processing via a CPU local lock.
> 
> As bottom halves are running always in thread context on RT kernels
> disabling preemption is the proper choice as it implicitly prevents bottom
> half processing.

I think someone sent a very similar looking patch in the past week or
two?