[ruby-core:114406] [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:
2023-08-18 14:32:40 UTC
List:
ruby-core #114406
Issue #19837 has been updated by jeremyevans0 (Jeremy Evans). Status changed from Open to Closed Backport changed from 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN to 3.0: UNKNOWN, 3.1: REQUIRED, 3.2: REQUIRED This updates the backport flags. Note that Ruby 3.0 is in security maintenance, and this doesn't appear to be security related, so it is unlikely to be backported to Ruby 3.0. ---------------------------------------- Bug #19837: Concurrent calls to Process.waitpid2 misbehave on Ruby 3.1 & 3.2 https://bugs.ruby-lang.org/issues/19837#change-104156 * Author: kjtsanaktsidis (KJ Tsanaktsidis) * Status: Closed * Priority: Normal * ruby -v: ruby 3.1.4p236 (2023-07-26 revision a8670865c0) [arm64-darwin22] * Backport: 3.0: UNKNOWN, 3.1: REQUIRED, 3.2: REQUIRED ---------------------------------------- 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/