From: lars@greiz-reinsdorf.de
To: ruby-core@ruby-lang.org
Subject: [ruby-core:89606] [Ruby trunk Bug#15262] GCing of object in use
Date: Sun, 28 Oct 2018 11:52:46 +0000 (UTC) [thread overview]
Message-ID: <redmine.journal-74643.20181028115245.775d5f9234c29e10@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-15262.20181027171221@ruby-lang.org
Issue #15262 has been updated by larskanis (Lars Kanis).
Thanks @nobu for looking at the issue!
> This method doesn't wait these threads which run start_adder.
It does: `initialize` waits for all threads to have called `Adder#add` at the last line at `@qu.deq` . It only returns after this event.
----------------------------------------
Bug #15262: GCing of object in use
https://bugs.ruby-lang.org/issues/15262#change-74643
* 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/
next prev parent reply other threads:[~2018-10-28 11:52 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <redmine.issue-15262.20181027171221@ruby-lang.org>
2018-10-27 17:12 ` [ruby-core:89579] [Ruby trunk Bug#15262] GCing of object in use lars
2018-10-28 10:39 ` [ruby-core:89602] [Ruby trunk Bug#15262][Feedback] " nobu
2018-10-28 11:52 ` lars [this message]
2018-10-29 1:13 ` [ruby-core:89610] [Ruby trunk Bug#15262] " nobu
2018-10-29 9:00 ` [ruby-core:89617] " lars
2018-10-30 1:34 ` [ruby-core:89625] " nobu
2018-10-30 15:08 ` [ruby-core:89643] [Ruby trunk Bug#15262] WeakRef::RefError for object that is still " lars
2018-10-30 16:16 ` [ruby-core:89646] " merch-redmine
2018-10-31 10:07 ` [ruby-core:89658] " lars
2020-01-14 11:13 ` [ruby-core:96852] [Ruby master " lars
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