Crash on shutdown in `dispatch_awaiting_callers`

[digitalcora]

I noticed a flaky test failure with the reason ** (exit) shutdown, and the following output logged:

** (stop) exited in: GenServer.stop(:normal, :normal, :infinity)
    ** (EXIT) no process: the process is not alive or there's no process currently associated with the given name, possibly because its application isn't started
    (elixir 1.12.1) lib/gen_server.ex:972: GenServer.stop/3
    (bypass 2.1.0) lib/bypass/instance.ex:385: Bypass.Instance.dispatch_awaiting_callers/1
    (bypass 2.1.0) lib/bypass/instance.ex:62: Bypass.Instance.handle_info/2
    (stdlib 3.14) gen_server.erl:689: :gen_server.try_dispatch/4
    (stdlib 3.14) gen_server.erl:765: :gen_server.handle_msg/6
    (stdlib 3.14) proc_lib.erl:226: :proc_lib.init_p_do_apply/3

Looking at the referenced code, it seems GenServer.stop/3 is not being called correctly: the first argument is supposed to be a reference to a server, but the Bypass code is GenServer.stop(:normal). So if there are any callers_awaiting_exit, this code will always crash.

[zraul123]

Any updates on this? We're seeing the same behavior causing flaky tests. Lately, for some reason, it started failing fairly often.

[firestack]

We've been having this happen more frequently (almost every CI run, rarely when run locally) since we updated to elixir 1.15.

I've tried fixing this locally by changing the GenServer.stop/3 call to be GenServer.stop(__MODULE__, :normal) in a local checkout, but I'm still having the issue where the test fails with ** (exit) shutdown, so while this needs to be fixed, I'm not sure it's the root cause of the test failure.

[grzuy]

Cross linking with opened pull requests that are attempting to fix this issue (I think):

• Stop Bypass.Instance correctly in dispatch_awaiting_callers/1 #141
• Fix incorrect GenServer.stop usage in Instance.dispatch_awaiting_callers #146