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List: ruby-core
Subject: [ruby-core:89602] [Ruby trunk Bug#15262][Feedback] GCing of object in use
From: nobu () ruby-lang ! org
Date: 2018-10-28 10:39:59
Message-ID: redmine.journal-74639.20181028103957.07bfef95f2875212 () ruby-lang ! org
[Download RAW message or body]
Issue #15262 has been updated by nobu (Nobuyoshi Nakada).
Description updated
Status changed from Open to Feedback
larskanis (Lars Kanis) wrote:
> Although `start_adder` works with a `WeakRef`, the `Adder` object should still be \
> GC marked, since `Adder.new` doesn't return before all calls to `start_adder` \
> finished.
> ```ruby
> @count.times do
> Thread.new(WeakRef.new(self), &self.class.method(:start_adder))
> end
This method doesn't wait these threads which run `start_adder`.
> ## Actual behavior:
>
> The program stops with a probability of approximately 80% with the following error:
So this behavior seems expected.
----------------------------------------
Bug #15262: GCing of object in use
https://bugs.ruby-lang.org/issues/15262#change-74639
* Author: larskanis (Lars Kanis)
* Status: Feedback
* Priority: Normal
* Assignee:
* Target version:
* ruby -v: ruby 2.6.0dev (2018-10-27 trunk 65390) [x86_64-linux]
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
----------------------------------------
Given the following program:
```ruby
require "weakref"
Thread.abort_on_exception = true
class Adder
def self.start_adder(obj)
obj.add
end
def initialize
@qu = Queue.new
@mutex = Mutex.new
@mutex.lock
begin
@count = 10
@count.times do
Thread.new(WeakRef.new(self), &self.class.method(:start_adder))
end
ensure
@mutex.unlock
end
@qu.deq
end
def add
@mutex.lock
begin
@count-=1
if @count == 0
@qu.enq true
elsif @count < 0
raise "shouldn't happen"
end
ensure
@mutex.unlock
end
end
end
def test_adder
10.times.map do
Thread.new do
Adder.new
end
end.each(&:join)
end
100.times do
test_adder
end
```
## Expected behaviour:
The program should simply execute without error. This is the case on JRuby but not on \
MRI.
## Actual behavior:
The program stops with a probability of approximately 80% with the following error:
```
$ ruby -W2 adder-test.rb
#<Thread:0x0000562d5089fea8@adder-test.rb:6 run> terminated with exception \
(report_on_exception is true): Traceback (most recent call last):
adder-test.rb:7:in `start_adder': Invalid Reference - probably recycled \
(WeakRef::RefError) Traceback (most recent call last):
adder-test.rb:7:in `start_adder': Invalid Reference - probably recycled \
(WeakRef::RefError) ```
Although `start_adder` works with a `WeakRef`, the `Adder` object should still be GC \
marked, since `Adder.new` doesn't return before all calls to `start_adder` finished.
I verified this on ruby-trunk, but get mostly the same behavior on all older MRI \
versions.
--
https://bugs.ruby-lang.org/
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