Bug #163: Thread.priority= is effectively a no-op

• Status: Closed
• Assignee: ko1 (Koichi Sasada)
• Target version: -

[pragdave (Dave Thomas)]

=begin
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?
=end

[ko1 (Koichi Sasada)]

• Assignee set to mame (Yusuke Endoh)

=begin

=end

[mame (Yusuke Endoh)]

• Assignee changed from mame (Yusuke Endoh) to ko1 (Koichi Sasada)

=begin
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 :-)
=end

[mame (Yusuke Endoh)]

• Status changed from Open to Closed

=begin
Applied in changeset r18570.
=end