[ruby-core:117882] [Ruby master Bug#20490] Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process

[ruby-core:117882] [Ruby master Bug#20490] Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process

[stanhu (Stan Hu) via ruby-core]

Issue #20490 has been reported by stanhu (Stan Hu).

----------------------------------------
Bug #20490: Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process
https://bugs.ruby-lang.org/issues/20490

* Author: stanhu (Stan Hu)
* Status: Open
* ruby -v: ruby 3.2.4 (2024-04-23 revision af471c0e01) [x86_64-linux]
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
This is a follow-up issue for a bug that I thought was fixed in https://bugs.ruby-lang.org/issues/19837 and duplicated in https://bugs.ruby-lang.org/issues/20181.

The following script doesn't terminate quickly in Ruby 3.1.5 and 3.2.4, even with the patches to address https://bugs.ruby-lang.org/issues/19837. It works fine in Ruby 3.3. It appears that the `Process::WNOHANG` argument passed to `Process.wait2` causes this script to spin until the child process stops:
 
```ruby
#!/bin/env ruby

Process.spawn({}, "sh -c 'sleep 600'").tap do |pid|
  puts "detaching PID #{pid}"
  Process.detach(pid)
end

forked_pid = fork do
  loop { sleep 1 }
end

child_waiter = Thread.new do
  puts "Waiting for child process to die..."

  # The spawned process has to exit before this returns in Ruby 3.1 and 3.2
  loop do
    pid, status = Process.wait2(-1, Process::WNOHANG)

    puts "Exited PID: #{pid}, status: #{status}"

    break if pid
    sleep 1
  end
end

process_killer = Thread.new do
  puts "Killing #{forked_pid}"
  system("kill #{forked_pid}")
end

child_waiter.join
process_killer.join
```

If I drop the `Process::WNOHANG` argument, it works fine.



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[ruby-core:117883] [Ruby master Bug#20490] Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process

[stanhu (Stan Hu) via ruby-core]

Issue #20490 has been updated by stanhu (Stan Hu).


I think this patch in the `ruby_3_2` branch fixes the problem:

```diff
diff --git a/process.c b/process.c
index 354e16fd26..bcf7f5aaf4 100644
--- a/process.c
+++ b/process.c
@@ -1291,6 +1299,9 @@ waitpid_wait(struct waitpid_state *w)
         if (w->ret == -1) w->errnum = errno;
     }
     else if (w->options & WNOHANG) {
+        if (w->pid < 0) {
+            need_sleep = TRUE;
+        }
     }
     else {
         need_sleep = TRUE;
```


----------------------------------------
Bug #20490: Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process
https://bugs.ruby-lang.org/issues/20490#change-108298

* Author: stanhu (Stan Hu)
* Status: Open
* ruby -v: ruby 3.2.4 (2024-04-23 revision af471c0e01) [x86_64-linux]
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
This is a follow-up issue for a bug that I thought was fixed in https://bugs.ruby-lang.org/issues/19837 and duplicated in https://bugs.ruby-lang.org/issues/20181.

The following script doesn't terminate quickly in Ruby 3.1.5 and 3.2.4, even with the patches to address https://bugs.ruby-lang.org/issues/19837. It works fine in Ruby 3.3. It appears that the `Process::WNOHANG` argument passed to `Process.wait2` causes this script to spin until the child process stops:
 
```ruby
#!/bin/env ruby

Process.spawn({}, "sh -c 'sleep 600'").tap do |pid|
  puts "detaching PID #{pid}"
  Process.detach(pid)
end

forked_pid = fork do
  loop { sleep 1 }
end

child_waiter = Thread.new do
  puts "Waiting for child process to die..."

  # The spawned process has to exit before this returns in Ruby 3.1 and 3.2
  loop do
    pid, status = Process.wait2(-1, Process::WNOHANG)

    puts "Exited PID: #{pid}, status: #{status}"

    break if pid
    sleep 1
  end
end

process_killer = Thread.new do
  puts "Killing #{forked_pid}"
  system("kill #{forked_pid}")
end

child_waiter.join
process_killer.join
```

If I drop the `Process::WNOHANG` argument, it works fine.



-- 
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[ruby-core:117884] [Ruby master Bug#20490] Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process

[stanhu (Stan Hu) via ruby-core]

Issue #20490 has been updated by stanhu (Stan Hu).


I've opened fixes here:

* 3.2: https://github.com/ruby/ruby/pull/10771
* 3.1: https://github.com/ruby/ruby/pull/10772

----------------------------------------
Bug #20490: Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process
https://bugs.ruby-lang.org/issues/20490#change-108299

* Author: stanhu (Stan Hu)
* Status: Open
* ruby -v: ruby 3.2.4 (2024-04-23 revision af471c0e01) [x86_64-linux]
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
This is a follow-up issue for a bug that I thought was fixed in https://bugs.ruby-lang.org/issues/19837 and duplicated in https://bugs.ruby-lang.org/issues/20181.

The following script doesn't terminate quickly in Ruby 3.1.5 and 3.2.4, even with the patches to address https://bugs.ruby-lang.org/issues/19837. It works fine in Ruby 3.3. It appears that the `Process::WNOHANG` argument passed to `Process.wait2` causes this script to spin until the child process stops:
 
```ruby
#!/bin/env ruby

Process.spawn({}, "sh -c 'sleep 600'").tap do |pid|
  puts "detaching PID #{pid}"
  Process.detach(pid)
end

forked_pid = fork do
  loop { sleep 1 }
end

child_waiter = Thread.new do
  puts "Waiting for child process to die..."

  # The spawned process has to exit before this returns in Ruby 3.1 and 3.2
  loop do
    pid, status = Process.wait2(-1, Process::WNOHANG)

    puts "Exited PID: #{pid}, status: #{status}"

    break if pid
    sleep 1
  end
end

process_killer = Thread.new do
  puts "Killing #{forked_pid}"
  system("kill #{forked_pid}")
end

child_waiter.join
process_killer.join
```

If I drop the `Process::WNOHANG` argument, it works fine.



-- 
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[ruby-core:117894] [Ruby master Bug#20490] Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process

[nagachika (Tomoyuki Chikanaga) via ruby-core]

Issue #20490 has been updated by nagachika (Tomoyuki Chikanaga).

Backport changed from 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN to 3.1: WONTFIX, 3.2: REQUIRED, 3.3: DONTNEED

Thank you for your report. I will look the PRs.
I will set the status of this ticket because of this is a backport ticket.
And currently 3.1 branch is under the security maintenance phase, so I fill the Backport field for 3.1 with "WONTFIX". cc: @hsbt (as the new 3.1 branch maintainer).

----------------------------------------
Bug #20490: Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process
https://bugs.ruby-lang.org/issues/20490#change-108310

* Author: stanhu (Stan Hu)
* Status: Open
* ruby -v: ruby 3.2.4 (2024-04-23 revision af471c0e01) [x86_64-linux]
* Backport: 3.1: WONTFIX, 3.2: REQUIRED, 3.3: DONTNEED
----------------------------------------
This is a follow-up issue for a bug that I thought was fixed in https://bugs.ruby-lang.org/issues/19837 and duplicated in https://bugs.ruby-lang.org/issues/20181.

The following script doesn't terminate quickly in Ruby 3.1.5 and 3.2.4, even with the patches to address https://bugs.ruby-lang.org/issues/19837. It works fine in Ruby 3.3. It appears that the `Process::WNOHANG` argument passed to `Process.wait2` causes this script to spin until the child process stops:
 
```ruby
#!/bin/env ruby

Process.spawn({}, "sh -c 'sleep 600'").tap do |pid|
  puts "detaching PID #{pid}"
  Process.detach(pid)
end

forked_pid = fork do
  loop { sleep 1 }
end

child_waiter = Thread.new do
  puts "Waiting for child process to die..."

  # The spawned process has to exit before this returns in Ruby 3.1 and 3.2
  loop do
    pid, status = Process.wait2(-1, Process::WNOHANG)

    puts "Exited PID: #{pid}, status: #{status}"

    break if pid
    sleep 1
  end
end

process_killer = Thread.new do
  puts "Killing #{forked_pid}"
  system("kill #{forked_pid}")
end

child_waiter.join
process_killer.join
```

If I drop the `Process::WNOHANG` argument, it works fine.



-- 
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 ______________________________________________
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[ruby-core:118648] [Ruby master Bug#20490] Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process

[nagachika (Tomoyuki Chikanaga) via ruby-core]

Issue #20490 has been updated by nagachika (Tomoyuki Chikanaga).


Currently the backport PR for ruby_3_2 was made by @kjtsanaktsidis.
https://github.com/ruby/ruby/pull/10787
But in my understanding, it was still in the works.

----------------------------------------
Bug #20490: Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process
https://bugs.ruby-lang.org/issues/20490#change-109176

* Author: stanhu (Stan Hu)
* Status: Closed
* ruby -v: ruby 3.2.4 (2024-04-23 revision af471c0e01) [x86_64-linux]
* Backport: 3.1: WONTFIX, 3.2: REQUIRED, 3.3: DONTNEED
----------------------------------------
This is a follow-up issue for a bug that I thought was fixed in https://bugs.ruby-lang.org/issues/19837 and duplicated in https://bugs.ruby-lang.org/issues/20181.

The following script doesn't terminate quickly in Ruby 3.1.5 and 3.2.4, even with the patches to address https://bugs.ruby-lang.org/issues/19837. It works fine in Ruby 3.3. It appears that the `Process::WNOHANG` argument passed to `Process.wait2` causes this script to spin until the child process stops:
 
```ruby
#!/bin/env ruby

Process.spawn({}, "sh -c 'sleep 600'").tap do |pid|
  puts "detaching PID #{pid}"
  Process.detach(pid)
end

forked_pid = fork do
  loop { sleep 1 }
end

child_waiter = Thread.new do
  puts "Waiting for child process to die..."

  # The spawned process has to exit before this returns in Ruby 3.1 and 3.2
  loop do
    pid, status = Process.wait2(-1, Process::WNOHANG)

    puts "Exited PID: #{pid}, status: #{status}"

    break if pid
    sleep 1
  end
end

process_killer = Thread.new do
  puts "Killing #{forked_pid}"
  system("kill #{forked_pid}")
end

child_waiter.join
process_killer.join
```

If I drop the `Process::WNOHANG` argument, it works fine.



-- 
https://bugs.ruby-lang.org/
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[ruby-core:118815] [Ruby master Bug#20490] Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process

[kjtsanaktsidis (KJ Tsanaktsidis) via ruby-core]

Issue #20490 has been updated by kjtsanaktsidis (KJ Tsanaktsidis).


Apologies I missed this - I just rebased the branch, I think it should be OK for a stable backport to 3.2. 

----------------------------------------
Bug #20490: Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process
https://bugs.ruby-lang.org/issues/20490#change-109373

* Author: stanhu (Stan Hu)
* Status: Closed
* ruby -v: ruby 3.2.4 (2024-04-23 revision af471c0e01) [x86_64-linux]
* Backport: 3.1: WONTFIX, 3.2: REQUIRED, 3.3: DONTNEED
----------------------------------------
This is a follow-up issue for a bug that I thought was fixed in https://bugs.ruby-lang.org/issues/19837 and duplicated in https://bugs.ruby-lang.org/issues/20181.

The following script doesn't terminate quickly in Ruby 3.1.5 and 3.2.4, even with the patches to address https://bugs.ruby-lang.org/issues/19837. It works fine in Ruby 3.3. It appears that the `Process::WNOHANG` argument passed to `Process.wait2` causes this script to spin until the child process stops:
 
```ruby
#!/bin/env ruby

Process.spawn({}, "sh -c 'sleep 600'").tap do |pid|
  puts "detaching PID #{pid}"
  Process.detach(pid)
end

forked_pid = fork do
  loop { sleep 1 }
end

child_waiter = Thread.new do
  puts "Waiting for child process to die..."

  # The spawned process has to exit before this returns in Ruby 3.1 and 3.2
  loop do
    pid, status = Process.wait2(-1, Process::WNOHANG)

    puts "Exited PID: #{pid}, status: #{status}"

    break if pid
    sleep 1
  end
end

process_killer = Thread.new do
  puts "Killing #{forked_pid}"
  system("kill #{forked_pid}")
end

child_waiter.join
process_killer.join
```

If I drop the `Process::WNOHANG` argument, it works fine.



-- 
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[ruby-core:118876] [Ruby master Bug#20490] Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process

[nagachika (Tomoyuki Chikanaga) via ruby-core]

Issue #20490 has been updated by nagachika (Tomoyuki Chikanaga).

Backport changed from 3.1: WONTFIX, 3.2: REQUIRED, 3.3: DONTNEED to 3.1: WONTFIX, 3.2: DONE, 3.3: DONTNEED

Merged at https://github.com/ruby/ruby/commit/65fed1c3e439bc47bcf6ec884431a86cb9ebd1dc. Thank you!

----------------------------------------
Bug #20490: Process.waitpid2(-1, Process::WNOHANG) misbehaves on Ruby 3.1 & 3.2 with detached process
https://bugs.ruby-lang.org/issues/20490#change-109448

* Author: stanhu (Stan Hu)
* Status: Closed
* ruby -v: ruby 3.2.4 (2024-04-23 revision af471c0e01) [x86_64-linux]
* Backport: 3.1: WONTFIX, 3.2: DONE, 3.3: DONTNEED
----------------------------------------
This is a follow-up issue for a bug that I thought was fixed in https://bugs.ruby-lang.org/issues/19837 and duplicated in https://bugs.ruby-lang.org/issues/20181.

The following script doesn't terminate quickly in Ruby 3.1.5 and 3.2.4, even with the patches to address https://bugs.ruby-lang.org/issues/19837. It works fine in Ruby 3.3. It appears that the `Process::WNOHANG` argument passed to `Process.wait2` causes this script to spin until the child process stops:
 
```ruby
#!/bin/env ruby

Process.spawn({}, "sh -c 'sleep 600'").tap do |pid|
  puts "detaching PID #{pid}"
  Process.detach(pid)
end

forked_pid = fork do
  loop { sleep 1 }
end

child_waiter = Thread.new do
  puts "Waiting for child process to die..."

  # The spawned process has to exit before this returns in Ruby 3.1 and 3.2
  loop do
    pid, status = Process.wait2(-1, Process::WNOHANG)

    puts "Exited PID: #{pid}, status: #{status}"

    break if pid
    sleep 1
  end
end

process_killer = Thread.new do
  puts "Killing #{forked_pid}"
  system("kill #{forked_pid}")
end

child_waiter.join
process_killer.join
```

If I drop the `Process::WNOHANG` argument, it works fine.



-- 
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 ______________________________________________
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 To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org
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