From: eregontp@...
Date: 2020-05-14T13:37:02+00:00
Subject: [ruby-core:98355] [Ruby master Bug#16889] TracePoint.enable { ... } also activates the TracePoint for other threads, even outside the block

Issue #16889 has been reported by Eregon (Benoit Daloze).

----------------------------------------
Bug #16889: TracePoint.enable { ... } also activates the TracePoint for other threads, even outside the block
https://bugs.ruby-lang.org/issues/16889

* Author: Eregon (Benoit Daloze)
* Status: Open
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
* ruby -v: ruby 2.6.6p146 (2020-03-31 revision 67876) [x86_64-linux]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
```ruby
threads = []
inspects = []
trace = TracePoint.new(:line) do |tp|
  threads << Thread.current
  inspects << tp.inspect
end

done = false
thread = Thread.new do
  Thread.pass until done
end

trace.enable do
  line_event = true
  done = true
  sleep 1
end
thread.join

# Expected only within enable block (lines 14-16)
puts inspects

# Expected just 1
p threads.uniq
```

Results in:
```
$ ruby tpbug.rb
ruby tpbug.rb
#<TracePoint:line@tpbug.rb:14>
#<TracePoint:line@tpbug.rb:15>
#<TracePoint:line@tpbug.rb:16>
#<TracePoint:line@tpbug.rb:10>
[#<Thread:0x00005571134e3340 run>, #<Thread:0x00005571138ac828@tpbug.rb:9 dead>]
```

But I expected:
```
#<TracePoint:line@tpbug.rb:14>
#<TracePoint:line@tpbug.rb:15>
#<TracePoint:line@tpbug.rb:16>
[#<Thread:0x00005571134e3340 run>]
```

For background I'm trying to improve the TracePoint specs in ruby/spec, but they are proving quite unreliable due to this.

@ko1 Thoughts?



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