On Wed, Dec 22, 2021 at 12:41:09PM +0100, Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote: > The sections with disabled preemption must exclude > memcg_check_events() so that spinlock_t locks can still be acquired > (for instance in eventfd_signal()). The resulting construct in uncharge_batch() raises eybrows. If you can decouple per-cpu updates from memcg_check_events() on PREEMPT_RT, why not tackle it the same way on !PREEMPT_RT too (and have just one variant of the block)? (Actually, it doesn't seem to me that memcg_check_events() can be extracted like this from the preempt disabled block since mem_cgroup_event_ratelimit() relies on similar RMW pattern. Things would be simpler if PREEMPT_RT didn't allow the threshold event handlers (akin to Michal Hocko's suggestion of rejecting soft limit).) Thanks, Michal
