On Mon, Feb 22, 2021 at 05:20:10PM -0800, Song Liu wrote:

BPF helpers bpf_task_storage_[get|delete] could hold two locks:
bpf_local_storage_map_bucket->lock and bpf_local_storage->lock. Calling
these helpers from fentry/fexit programs on functions in bpf_*_storage.c
may cause deadlock on either locks.

Prevent such deadlock with a per cpu counter, bpf_task_storage_busy, which
is similar to bpf_prog_active. We need this counter to be global, because

So bpf_prog_active is one of the biggest turds around, and now you're
making it worse ?!