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Bug #20587

closed

dir.c calls blocking filesystem APIs/system calls while holding the GVL

Added by ivoanjo (Ivo Anjo) 5 months ago. Updated 4 months ago.

Status:
Closed
Assignee:
-
Target version:
-
[ruby-core:118347]

Description

Hey! I work for Datadog on the Ruby profiler part of the datadog (previously ddtrace) gem.

While I was investigating https://bugs.ruby-lang.org/issues/20586, I spotted that there's a number of cases where, in dir.c, blocking system calls are being made (e.g. readdir(), opendir(), ... see comments for more detailed list...) without releasing the GVL.

This means that if they block for a long time (as happens in the gcsfuse example in https://bugs.ruby-lang.org/issues/20586 ), the Ruby VM will just be blocked and not make any progress.

The combination of not releasing the GVL + slow system calls actually makes the issue in https://bugs.ruby-lang.org/issues/20586 more likely to happen with the Datadog profiler, although even if the code releases the GVL the underlying issue could still happen, and this is why I decided to file this bug separately.


Files

repro.rb (1.18 KB) repro.rb ivoanjo (Ivo Anjo), 07/12/2024 11:31 AM
hello.c (4.89 KB) hello.c ivoanjo (Ivo Anjo), 07/12/2024 11:33 AM
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