# \[Ruby 1.9 - Bug #163\] (Open) Thread.priority= is effectively a no-op

**URL:** <https://www.ruby-forum.com/t/ruby-1-9-bug-163-open-thread-priority-is-effectively-a-no-op/140550>\
**Category:** Development\
**Created:** [June 16, 2008, 5:07am UTC](https://www.ruby-forum.com/t/ruby-1-9-bug-163-open-thread-priority-is-effectively-a-no-op/140550 "2008-06-16T05:07:14Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![dirtytree](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/aeb1de/32.png) [@dirtytree](https://www.ruby-forum.com/u/dirtytree)\
**Post date:** [June 16, 2008, 5:07am UTC](https://www.ruby-forum.com/t/ruby-1-9-bug-163-open-thread-priority-is-effectively-a-no-op/140550/1 "2008-06-16T05:07:14Z")

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e$B%A%1%C%He(B #163 e$B$,Js9p$5$l$^$7$?!#e(B (by Dave T.)

* * *

Bug #163: Thread.priority= is effectively a no-op  
[http://redmine.ruby-lang.org/issues/show/163](http://redmine.ruby-lang.org/issues/show/163)

e$B5/I\<\<Te(B: Dave T.  
e$B%9%F!\<%?%9e(B: Open  
e$BM%@hEYe(B: Normal  
e$BC4Ev\<Te(B:  
e$B%+%F%4%je(B:  
Target version:

I raised the following back in January:

Is it reasonable to expect the following to produce differing counts in  
the result array?

counts = [0] \* 10  
Thread.abort\_on\_exception = true  
10.times do |i|  
thread = Thread.new(i) do |index|  
Thread.current.priority = index  
loop do  
counts[index] += 1  
Thread.pass  
end  
end  
end  
sleep 1  
p counts

I get [6176, 6173, 6167, 6173, 6174, 6175, 6177, 6178, 6174, 6177]

Matz replied:

I don’t know the rationale behind, but at least on Linux:

- the default scheduling policy is SCHED\_OTHER. Ruby does not  
explicitly specify scheduling policy.
- for SCHED\_OTHER, min and max of priority is both zero
- the specified priority is rounded to zero
- as a result, no priority change happens

We have to ask Koichi if it’s a bug or not.

Given this: (a) is it a Ruby bug, and (b) if not, should we remove the  
method, as it might confuse folks?

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<div class="post-metadata">

**Author:** ![dirtytree](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/aeb1de/32.png) [@dirtytree](https://www.ruby-forum.com/u/dirtytree)\
**Post date:** [July 9, 2008, 1:20pm UTC](https://www.ruby-forum.com/t/ruby-1-9-bug-163-open-thread-priority-is-effectively-a-no-op/140550/2 "2008-07-09T13:20:14Z")

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e$B%A%1%C%He(B #163 e$B$,99?7$5$l$^$7$?!#e(B (by Yusuke E.)

e$BC4Ev\<Te(B Yusuke E.e$B$+$ie(BKoichi Sasadae$B$KJQ99e(B

I have three choice:

(1) make Thread#priority= deprecated (or remove)  
(2) add “Not available on all platforms.” to its document  
(3) very ad-hoc fix [ruby-dev:33124]  
(4) another way that I cannot think of

## Please select 🙂

[http://redmine.ruby-lang.org/issues/show/163](http://redmine.ruby-lang.org/issues/show/163)

---

<div class="post-metadata">

**Author:** ![dirtytree](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/aeb1de/32.png) [@dirtytree](https://www.ruby-forum.com/u/dirtytree)\
**Post date:** [August 21, 2008, 2:50pm UTC](https://www.ruby-forum.com/t/ruby-1-9-bug-163-open-thread-priority-is-effectively-a-no-op/140550/3 "2008-08-21T14:50:14Z")

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e$B%A%1%C%He(B #163 e$B$,99?7$5$l$^$7$?!#e(B (by Yusuke E.)

e$B%9%F!\<%?%9e(B Opene$B$+$ie(BClosede$B$KJQ99e(B

## Applied in changeset r18570.

[http://redmine.ruby-lang.org/issues/show/163](http://redmine.ruby-lang.org/issues/show/163)