The return value of LMCACHE_LAUNCH_HOST_FUNC (which maps to cudaLaunchHostFunc or hipLaunchHostFunc) is not checked. If the CUDA/HIP driver fails to schedule the host function, the event pointer allocated on line 64 will be leaked because the callback that normally deletes it will never run. You should check the return status and delete the event if it's not success (0).

  if (LMCACHE_LAUNCH_HOST_FUNC(stream, event_host_callback, event) != 0) {
    delete event;
  }

@ApostaC How about this suggestion?

Global singleton drain causes cross-instance event stealing

Low Severity

The _drain_all method drains events from the process-global C++ EventRecorder singleton. This allows events published through one EventBus instance to be consumed by any other instance, breaking per-instance isolation and leading to non-deterministic event dispatch.

 

^{Triggered by project rule: LMCache Code Review Style Guide}

^{Reviewed by Cursor Bugbot for commit 5b90164. Configure here.}

Global singleton EventRecorder causes cross-bus event leakage

Medium Severity

The _drain_all method in EventBus pulls events from a process-global C++ buffer. When multiple EventBus instances are active, any instance can drain all events from this shared buffer, which may lead to events being delivered to incorrect subscribers or lost entirely.

 

^{Triggered by project rule: LMCache Code Review Style Guide}

^{Reviewed by Cursor Bugbot for commit 5b90164. Configure here.}

Bool values misrouted due to int subclass check

Low Severity

In publish_on_stream, isinstance(v, int) returns True for bool values because Python's bool is a subclass of int. Any boolean metadata value silently enters int_metadata (as 1/0) and returns from _drain_all as a plain int, losing its original type. The old code path preserved all types unchanged. Adding isinstance(v, bool) before the int check (routing bools to str_metadata) would preserve round-trip fidelity for the dict[str, Any] metadata contract.

 

^{Reviewed by Cursor Bugbot for commit cde5d78. Configure here.}

Deadlock diagnostic function defined but never called

Medium Severity

The dump_stacks() helper function is defined to capture py-spy stack dumps for deadlock diagnosis, but it is never actually called anywhere in the script. When the benchmark times out (the exact scenario this test exists to catch), only the last 50 lines of logs are printed — the py-spy stack dump that would reveal the actual deadlock threads is never triggered. This defeats the purpose of installing py-spy and defining the function.

 

^{Reviewed by Cursor Bugbot for commit 5e4dccc. Configure here.}

Unchecked CUDA API return leaks memory on failure

Medium Severity

The return value of LMCACHE_LAUNCH_HOST_FUNC (cudaLaunchHostFunc/hipLaunchHostFunc) is not checked. If the call fails, the heap-allocated PendingEvent is never freed (the callback that would delete it never runs), and the error is silently swallowed. Other CUDA API calls in this codebase (e.g., in mem_alloc.cpp) consistently check return values and throw on failure.

 

^{Reviewed by Cursor Bugbot for commit a7b6bfd. Configure here.}