On Thu, Apr 06, 2017 at 01:03:16PM +0200, Thomas Gleixner wrote: > Fair enough, but I prefer to have the ability for a temporary restriction > of the user space visible cpus allowed mask in the core code, which can be > used for both migrate_disable() and things like that MIPS FPU stuff rather > than all those home brewn hackeries which are prone to bitrot, security > issues and subtle wreckage. cpus_allowed should be solely under sched core > control and not accessible from anything outside.
So the big difference between what MIPS does and what migrate_disable() needs here is the amount of storage. For migrate_disable() we don't need a whole second cpumask bitmap. We can simply use one of the static cpumask_of() things. Given that cpumask bitmaps can be quite large, adding another one to task_struct just for $very_rare_occasion, doesn't seem like a good thing.
