Bug #163

Thread.priority= is effectively a no-op

Added by Dave Thomas over 7 years ago. Updated over 4 years ago.

Assignee:Koichi Sasada
ruby -v: Backport:


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
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?


#1 Updated by Koichi Sasada about 7 years ago

  • Assignee set to Yusuke Endoh



#2 Updated by Yusuke Endoh about 7 years ago

  • Assignee changed from Yusuke Endoh to Koichi Sasada

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 another way that I cannot think of

Please select :-)

#3 Updated by Yusuke Endoh about 7 years ago

  • Status changed from Open to Closed

Applied in changeset r18570.

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