On Fri, Sep 05, 2025 at 02:20:46PM -0700, Roman Gushchin wrote: > Shakeel Butt <shakeel.butt@xxxxxxxxx> writes: > > > Generally memcg charging is allowed from all the contexts including NMI > > where even spinning on spinlock can cause locking issues. However one > > call chain was missed during the addition of memcg charging from any > > context support. That is try_charge_memcg() -> memcg_memory_event() -> > > cgroup_file_notify(). > > > > The possible function call tree under cgroup_file_notify() can acquire > > many different spin locks in spinning mode. Some of them are > > cgroup_file_kn_lock, kernfs_notify_lock, pool_workqeue's lock. So, let's > > just skip cgroup_file_notify() from memcg charging if the context does > > not allow spinning. > > Hmm, what about OOM events? Losing something like MEMCG_LOW doesn't look > like a bit deal, but OOM events can be way more important. > > Should we instead preserve the event (e.g. as a pending_event_mask) and > raise it on the next occasion / from a different context? > Thanks for the review. For now only MAX can happen in non-spinning context. All others only happen in process context. Maybe with BPF OOM, OOM might be possible in a different context (is that what you are thinking?). I think we can add the complexity of preserving the event when the actual need arise.
