On Tue, May 28, 2024 at 05:07:06PM GMT, Vlastimil Babka (SUSE) wrote: > On 5/28/24 4:59 PM, Shakeel Butt wrote: > > On Tue, May 28, 2024 at 04:13:41PM GMT, Sebastian Andrzej Siewior wrote: > >> The assert was introduced in the commit cited below as an insurance that > >> the semantic is the same after the local_irq_save() has been removed and > >> the function has been made static. > >> > >> The original requirement to disable interrupt was due the modification > >> of per-CPU counters which require interrupts to be disabled because the > >> counter update operation is not atomic and some of the counters are > >> updated from interrupt context. > >> > >> All callers of __mod_objcg_mlstate() acquire a lock > >> (memcg_stock.stock_lock) which disables interrupts on !PREEMPT_RT and > >> the lockdep assert is satisfied. On PREEMPT_RT the interrupts are not > >> disabled and the assert triggers. > >> > >> The safety of the counter update is already ensured by > >> VM_WARN_ON_IRQS_ENABLED() which is part of __mod_memcg_lruvec_state() and > >> does not require yet another check. > > > > One question on VM_WARN_ON_IRQS_ENABLED() in __mod_memcg_lruvec_state(). > > On a PREEMPT_RT kernel with CONFIG_DEBUG_VM, will that > > VM_WARN_ON_IRQS_ENABLED() cause a splat or VM_WARN_ON_IRQS_ENABLED is > > special on PREEMPT_RT kernels? > > It only does something with CONFIG_DEBUG_VM_IRQSOFF and that's disabled by > dependencies on PREEMPT_RT :) Thanks for the explanation.
