On Mon 08-09-25 10:11:29, Alexei Starovoitov wrote: > On Mon, Sep 8, 2025 at 2:08 AM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > On Fri 05-09-25 20:48:46, Peilin Ye wrote: > > > On Fri, Sep 05, 2025 at 01:16:06PM -0700, Shakeel Butt wrote: > > > > 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. > > > > > > > > Signed-off-by: Shakeel Butt <shakeel.butt@xxxxxxxxx> > > > > > > Tested-by: Peilin Ye <yepeilin@xxxxxxxxxx> > > > > > > The repro described in [1] no longer triggers locking issues after > > > applying this patch and making __bpf_async_init() use __GFP_HIGH > > > instead of GFP_ATOMIC: > > > > > > --- a/kernel/bpf/helpers.c > > > +++ b/kernel/bpf/helpers.c > > > @@ -1275,7 +1275,7 @@ static int __bpf_async_init(struct bpf_async_kern *async, struct bpf_map *map, u > > > } > > > > > > /* allocate hrtimer via map_kmalloc to use memcg accounting */ > > > - cb = bpf_map_kmalloc_node(map, size, GFP_ATOMIC, map->numa_node); > > > + cb = bpf_map_kmalloc_node(map, size, __GFP_HIGH, map->numa_node); > > > > Why do you need to consume memory reserves? Shouldn't kmalloc_nolock be > > used instead here? > > Yes. That's a plan. We'll convert most of bpf allocations to kmalloc_nolock() > when it lands. OK, I thought this was merged already. I suspect __GFP_HIGH is used here as a result of manual GFP_ATOMIC & ~GFP_RECLAIM. A TODO/FIXME referring to kmalloc_nolock would clarify the situation. -- Michal Hocko SUSE Labs
