[ruby-core:112155] [Ruby master Bug#19395] Process forking within non-main Ractor creates child stuck in busy loop
31 Jan
2023
31 Jan
'23
10:26 p.m.
Issue #19395 has been reported by luke-gru (Luke Gruber).
----------------------------------------
Bug #19395: Process forking within non-main Ractor creates child stuck in busy loop
https://bugs.ruby-lang.org/issues/19395
* Author: luke-gru (Luke Gruber)
* Status: Open
* Priority: Normal
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
```ruby
def test_fork_in_ractor
r2 = Ractor.new do
pid = fork do
exit Ractor.count
end
pid
end
pid = r2.take
puts "Process #{Process.pid} waiting for #{pid}"
_pid, status = Process.waitpid2(pid) # stuck forever
if status.exitstatus != 1
raise "status is #{status.exitstatus}"
end
end
test_fork_in_ractor()
```
$ top # shows CPU usage is high for child process
--
https://bugs.ruby-lang.org/
1 Feb
1 Feb
12:47 a.m.
New subject: [ruby-core:112157] [Ruby master Bug#19395] Process forking within non-main Ractor causes segv
Issue #19395 has been updated by luke-gru (Luke Gruber).
Subject changed from Process forking within non-main Ractor creates child stuck in busy
loop to Process forking within non-main Ractor causes segv
Sorry, my changes in my dev branch were causing some odd behavior. It just crashes on
3.2.0.
----------------------------------------
Bug #19395: Process forking within non-main Ractor causes segv
https://bugs.ruby-lang.org/issues/19395#change-101593
* Author: luke-gru (Luke Gruber)
* Status: Open
* Priority: Normal
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
```ruby
def test_fork_in_ractor
r2 = Ractor.new do
pid = fork do
exit Ractor.count
end
pid
end
pid = r2.take
puts "Process #{Process.pid} waiting for #{pid}"
_pid, status = Process.waitpid2(pid) # stuck forever
if status.exitstatus != 1
raise "status is #{status.exitstatus}"
end
end
test_fork_in_ractor()
```
$ top # shows CPU usage is high for child process
--
https://bugs.ruby-lang.org/
7:06 a.m.
New subject: [ruby-core:112164] [Ruby master Bug#19395] Process forking within non-main Ractor causes segv
Issue #19395 has been updated by nobu (Nobuyoshi Nakada).
luke-gru (Luke Gruber) wrote in #note-1:
It just crashes on 3.2.0.
I can't reproduce the SEGV on macOS 13.1.
What platform are you using?
----------------------------------------
Bug #19395: Process forking within non-main Ractor causes segv
https://bugs.ruby-lang.org/issues/19395#change-101600
* Author: luke-gru (Luke Gruber)
* Status: Open
* Priority: Normal
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
```ruby
def test_fork_in_ractor
r2 = Ractor.new do
pid = fork do
exit Ractor.count
end
pid
end
pid = r2.take
puts "Process #{Process.pid} waiting for #{pid}"
_pid, status = Process.waitpid2(pid) # stuck forever
if status.exitstatus != 1
raise "status is #{status.exitstatus}"
end
end
test_fork_in_ractor()
```
$ top # shows CPU usage is high for child process
--
https://bugs.ruby-lang.org/
1:38 p.m.
New subject: [ruby-core:112170] [Ruby master Bug#19395] Process forking within non-main Ractor causes segv
Issue #19395 has been updated by luke-gru (Luke Gruber).
ruby -v set to 3.2.0
Ubuntu 22.04, the issue seems to be calling `rb_native_mutex_destroy` on a locked mutex in
`ractor_free`.
Relevant part of the backtrace:
```
/home/lukeg/.rbenv/versions/3.2.0/lib/libruby.so.3.2(die+0x0) [0x7fc1374d0e5f]
/tmp/ruby-build.20230103230257.28392.jU9iPR/ruby-3.2.0/error.c:798
/home/lukeg/.rbenv/versions/3.2.0/lib/libruby.so.3.2(rb_bug)
/tmp/ruby-build.20230103230257.28392.jU9iPR/ruby-3.2.0/error.c:800
/home/lukeg/.rbenv/versions/3.2.0/lib/libruby.so.3.2(rb_bug_errno+0x43) [0x7fc137579223]
/tmp/ruby-build.20230103230257.28392.jU9iPR/ruby-3.2.0/error.c:829
/home/lukeg/.rbenv/versions/3.2.0/lib/libruby.so.3.2(rb_native_mutex_destroy+0x24)
[0x7fc137719a24]
/tmp/ruby-build.20230103230257.28392.jU9iPR/ruby-3.2.0/thread_pthread.c:603
/home/lukeg/.rbenv/versions/3.2.0/lib/libruby.so.3.2(ractor_free+0x11) [0x7fc137679991]
/tmp/ruby-build.20230103230257.28392.jU9iPR/ruby-3.2.0/ractor.c:235
/home/lukeg/.rbenv/versions/3.2.0/lib/libruby.so.3.2(run_final+0xf)
```
If instead you change `exit 0` to `exec "date"`, it doesn't crash. Maybe the
atfork hooks need to be changed to acquire locks in parent, unlock in child.
----------------------------------------
Bug #19395: Process forking within non-main Ractor causes segv
https://bugs.ruby-lang.org/issues/19395#change-101606
* Author: luke-gru (Luke Gruber)
* Status: Feedback
* Priority: Normal
* ruby -v: 3.2.0
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
```ruby
def test_fork_in_ractor
r2 = Ractor.new do
pid = fork do
exit Ractor.count
end
pid
end
pid = r2.take
puts "Process #{Process.pid} waiting for #{pid}"
_pid, status = Process.waitpid2(pid) # stuck forever
if status.exitstatus != 1
raise "status is #{status.exitstatus}"
end
end
test_fork_in_ractor()
```
$ top # shows CPU usage is high for child process
--
https://bugs.ruby-lang.org/
10:21 p.m.
New subject: [ruby-core:112175] [Ruby master Bug#19395] Process forking within non-main Ractor hits rb_bug()
Issue #19395 has been updated by luke-gru (Luke Gruber).
This fixes it:
https://github.com/luke-gru/ruby/commit/0cb53d4458eb09d8a3f70caaa44c688b48b…
The issue is that when there's multiple ractors and you call fork, the other ractor(s)
that are in the child process that aren't the new main ractor need to be GC'd, and
their mutexes could be in a weird state, so either skip destruction of them or
reinitialize them in the child process. Re-init works on my machine but I don't know
if it works across platforms.
----------------------------------------
Bug #19395: Process forking within non-main Ractor hits rb_bug()
https://bugs.ruby-lang.org/issues/19395#change-101612
* Author: luke-gru (Luke Gruber)
* Status: Feedback
* Priority: Normal
* ruby -v: 3.2.0
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
```ruby
def test_fork_in_ractor
r2 = Ractor.new do
pid = fork do
exit Ractor.count
end
pid
end
pid = r2.take
puts "Process #{Process.pid} waiting for #{pid}"
_pid, status = Process.waitpid2(pid) # stuck forever
if status.exitstatus != 1
raise "status is #{status.exitstatus}"
end
end
test_fork_in_ractor()
```
$ top # shows CPU usage is high for child process
--
https://bugs.ruby-lang.org/
16 Feb
16 Feb
7:19 p.m.
New subject: [ruby-core:116804] [Ruby master Bug#19395] Process forking within non-main Ractor hits rb_bug()
Issue #19395 has been updated by luke-gru (Luke Gruber).
I can no longer reproduce this issue, I probably had some changes in my tree that were
causing the issues. Sorry! Please close.
----------------------------------------
Bug #19395: Process forking within non-main Ractor hits rb_bug()
https://bugs.ruby-lang.org/issues/19395#change-106827
* Author: luke-gru (Luke Gruber)
* Status: Feedback
* Priority: Normal
* ruby -v: 3.2.0
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
```ruby
def test_fork_in_ractor
r2 = Ractor.new do
pid = fork do
exit Ractor.count
end
pid
end
pid = r2.take
puts "Process #{Process.pid} waiting for #{pid}"
_pid, status = Process.waitpid2(pid) # stuck forever
if status.exitstatus != 1
raise "status is #{status.exitstatus}"
end
end
test_fork_in_ractor()
```
$ top # shows CPU usage is high for child process
--
https://bugs.ruby-lang.org/
71
days inactive
452
days old
5 comments
2 participants
participants (2)
-
luke-gru (Luke Gruber) -
nobu (Nobuyoshi Nakada)