fix(expert_credo): prevent infinite hang in with_stdin/2#372
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This is part of a set of 4 PRs that arose out of some static analysis tooling I'm working on: - #369 - #370 - #371 - #372 That means that these aren't crashes or issues that I've observed in practice, however based on my reading of the code, they do represent issues worth addressing. ## Problem: `Beams.apply_to_all/2` spawns its worker process using a bare `spawn/1`, and then blocks in `block_until_done/3` until it receives a `:progress` message from it. If the worker crashes, this message will never arrive, and the caller will block indefinitely. ## Solution Replace `spawn/1` with `spawn_monitor/1`, and add a `receive` clause in `block_until_done/3` to handle the worker unexpectedly terminating before a `:progress` message is sent, so that we're able to immediately raise instead of blocking forever. In the successful case, the monitor is flushed to avoid `:DOWN` messages building up and causing a mailbox leak.
Replace bare spawn with spawn_monitor so the caller receives a
{:DOWN, ...} message if the spawned process crashes, instead of
blocking in receive forever.
Add a 30-second timeout as a safety net against indefinite hangs.
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This is part of a set of 4 PRs that arose out of some static analysis tooling I'm working on:
That means that these aren't crashes or issues that I've observed in practice, however based on my reading of the code, they do represent issues worth addressing.
Problem:
This is effectively the same issue as in #370, where the use of a bare
spawn/2causes the spawning process to hang indefinitely while waiting for a message from the spawned process, and preventingCredodiagnostics from being updated.Solution
Replace
spawn/1withspawn_monitor/1, and add areceiveclause to handle the spawned process unexpectedly terminating before sending a result.In the successful case, the monitor is flushed to avoid
:DOWNmessages building up and causing a mailbox leak.A 30 second timeout is also added, to prevent buggy or broken
Credomodules from causing the entire system to hang.