David suggested during the discussion in [0] that we should handle RCU locks in a similar fashion to spin locks where the verifier understands when a lock held in a caller is released in callee, or lock taken in callee is released in a caller, or the callee is called within a lock critical section. This set extends the same semantics to RCU read locks and adds a few selftests to verify correct behavior. This issue has also come up for sched-ext programs. This would now allow static subprog calls to be made without errors within RCU read sections, for subprogs to release RCU locks of callers and return to them, or for subprogs to take RCU lock which is later released in the caller. [0]: https://lore.kernel.org/bpf/20240204120206.796412-1-memxor@xxxxxxxxx Kumar Kartikeya Dwivedi (2): bpf: Transfer RCU lock state between subprog calls selftests/bpf: Add tests for RCU lock transfer between subprogs kernel/bpf/verifier.c | 3 +- .../selftests/bpf/prog_tests/rcu_read_lock.c | 3 + .../selftests/bpf/progs/rcu_read_lock.c | 64 +++++++++++++++++++ 3 files changed, 68 insertions(+), 2 deletions(-) base-commit: 2a79690eae953daaac232f93e6c5ac47ac539f2d -- 2.40.1
