[ruby-core:114397] [Ruby master Bug#19837] Concurrent calls to Process.waitpid2 misbehave on Ruby 3.1 & 3.2
From:
"jeremyevans0 (Jeremy Evans) via ruby-core" <ruby-core@...>
Date:
2023-08-17 22:08:37 UTC
List:
ruby-core #114397
Issue #19837 has been updated by jeremyevans0 (Jeremy Evans). @kjtsanaktsidis Yes, please prepare backport pull requests for ruby_3_2 and ruby_3_1, then we can update the backport flags in this issue to let the branch maintainer know it is ready for backporting. ---------------------------------------- Bug #19837: Concurrent calls to Process.waitpid2 misbehave on Ruby 3.1 & 3.2 https://bugs.ruby-lang.org/issues/19837#change-104149 * Author: kjtsanaktsidis (KJ Tsanaktsidis) * Status: Open * Priority: Normal * ruby -v: ruby 3.1.4p236 (2023-07-26 revision a8670865c0) [arm64-darwin22] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- On Ruby 3.1 & 3.2, if you have one thread blocked into a directed call to `Process.waitpid2` with a pid specified, a concurrent call to `Process.waitpid2 -1` will not be able to find & reap any other terminated child process, even one with a different pid that is not individually being waited on. I've attached a Ruby program which should terminate but doesn't as a result of this bug, as well as a C program which demonstrates that the underlying syscalls (at least on Linux) do behave how you would expect. My reproduction creates two processes; a long-running process that does not exit, and a short one which does. There is a background thread calling `Process.waitpid2` on the long process. Then, a concurrent call to `Process.waitpid2 -1` does not notice that the short-running process has exited. My `wait_bug.rb` program _does_ work properly and terminate on the current master branch of Ruby; I assume this is because all of the MJIT-related process management stuff with the waiting_pids & stuff has been cleaned up as part of the MJIT -> RJIT refactoring. Because of this, I'm not sure exactly how to make a patch; should I open a pair of PRs targeting the `ruby_3_2` and `ruby_3_1` branch? Thanks! ---Files-------------------------------- wait_bug.c (1.55 KB) wait_bug.rb (735 Bytes) -- https://bugs.ruby-lang.org/ ______________________________________________ ruby-core mailing list -- ruby-core@ml.ruby-lang.org To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org ruby-core info -- https://ml.ruby-lang.org/mailman3/postorius/lists/ruby-core.ml.ruby-lang.org/