From: ko1@...
Date: 2014-11-25T07:58:32+00:00
Subject: [ruby-core:66455] [ruby-trunk - Bug #10540] Yielded fibers do not	execute ensure blocks

Issue #10540 has been updated by Koichi Sasada.

Assignee set to Koichi Sasada
Target version set to next minor

This issue is a known bug.
[Bug #595]: Fiber ignores ensure clause
(3 digits!)

Rubinius supports it.

----

This feature is not impossible, but a bit difficult because there are two ENSURE points.

(1) Owner thread is terminated.
(2) Fiber object is collected.

In this issue, (1) is pointed out. It is easy to implement by sending EXIT exception for owned fibers.
However, (2) is a problem. We can not use finalizers for each fibers because it is too late (in finalizer, Fiber object should be already terminated). To solve this issue, we need to separate fiber handler and fiber cotext itself. In other words, it is possible, but tough hack.

And another issue is compatibility. It is too late to fix this issue for 2.2.
I try to implement this fix and apply in early 2015.

----------------------------------------
Bug #10540: Yielded fibers do not execute ensure blocks
https://bugs.ruby-lang.org/issues/10540#change-50078

* Author: Yehuda Katz
* Status: Open
* Priority: Normal
* Assignee: Koichi Sasada
* Category: 
* Target version: next minor
* ruby -v: ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-darwin13.0]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN
----------------------------------------
When a thread has paused fibers, if an exception occurs anywhere in the thread, `ensure` blocks in the paused fibers do not execute.

The effect of this is that block-scoped resources (like File.open, Mutex#synchronize, ActiveRecord transactions) can easily leak due to non-local effects. This may result in strange effects, like checking connections back into a connection pool that are in the wrong state, where the correct state was guarded with an `ensure` block.

Here is a very simple repro of this situation:

~~~
Thread.new {
  Fiber.new {
    begin
      puts "YIELD"
      Fiber.yield
    ensure
      puts "UNWIND"
    end
  }.resume
  raise
}
~~~

Expected result: `YIELD` is printed, followed by `UNWIND`
Actual result: `YIELD` is printed, but `UNWIND` is never printed



-- 
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