Re: [PATCH bpf-next v4 1/4] bpf: Add a sleepable page allocator for map memory

[Michal Hocko]

On Fri 21-08-26 13:06:12, Jiayuan Chen wrote:
> bpf_map_alloc_pages() picks the allocator via can_alloc_pages(), a
> conservative guess for BPF program context that is always false under
> PREEMPT_RT. So even a caller that really is sleepable gets the
> non-blocking allocator, which never reclaims and never engages the OOM
> machinery.

I thought one of the main motivations was reentrancy. As you cannot
really assume the context bpf_map_alloc_pages is called from there is an
extra care needed so that this doesn't re-enter the allocator from bpf
program called from allocator path and deadlock.

-- 
Michal Hocko
SUSE Labs