On 12/22/21 06:41, Sebastian Andrzej Siewior wrote:
The per-CPU counter are modified with the non-atomic modifier. The consistency is ensure by disabling interrupts for the update. This breaks on PREEMPT_RT because some sections additionally acquire a spinlock_t lock (which becomes sleeping and must not be acquired with disabled interrupts). Another problem is that mem_cgroup_swapout() expects to be invoked with disabled interrupts because the caller has to acquire a spinlock_t which is acquired with disabled interrupts. Since spinlock_t never disables interrupts on PREEMPT_RT the interrupts are never disabled at this point. The code is never called from in_irq() context on PREEMPT_RT therefore
How do you guarantee that these percpu update functions won't be called in in_irq() context for PREEMPT_RT? Do you think we should add a WARN_ON_ONCE(in_irq()) just to be sure?
Cheers, Longman
