Method unlock

system/lib/llvm-libc/shared/rpc.h:211–221

Unlock the lock at index. We need a lane sync to keep this function convergent, otherwise the compiler will sink the store and deadlock.

  /// Unlock the lock at index. We need a lane sync to keep this function
  /// convergent, otherwise the compiler will sink the store and deadlock.
  RPC_ATTRS void unlock(uint64_t lane_mask, uint32_t index) {
    // Do not move any writes past the unlock.
    __scoped_atomic_thread_fence(__ATOMIC_RELEASE, __MEMORY_SCOPE_DEVICE);

    // Use exactly one thread to clear the nth bit in the lock array Must
    // restrict to a single thread to avoid one thread dropping the lock, then
    // an unrelated warp claiming the lock, then a second thread in this warp
    // dropping the lock again.
    clear_nth(lock, index, rpc::is_first_lane(lane_mask));
    rpc::sync_lane(lane_mask);
  }

  /// Number of bytes to allocate for an inbox or outbox.
  RPC_ATTRS static constexpr uint64_t mailbox_bytes(uint32_t port_count) {