[ruby-core:107076] [Ruby master Bug#18482] Fiber can not disable scheduler

Issue #18482 has been reported by jakit (Jakit Liang).

----------------------------------------
Bug #18482: Fiber can not disable scheduler
https://bugs.ruby-lang.org/issues/18482

* Author: jakit (Jakit Liang)
* Status: Open
* Priority: Normal
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
class Fiber can not disable scheduler with it's parameter.

When parameter is `false`:

```
require 'fiber'
require 'io/nonblock'

class SimpleScheduler
  def initialize
    @readable = {}
    @writable = {}
    @waiting = {}
    @ready = []
    @blocking = 0
    @urgent = IO.pipe
  end

  def run
    while @readable.any? or @writable.any? or @waiting.any? or @blocking.positive? or @ready.any?
      readable, writable = IO.select(@readable.keys + [@urgent.first], @writable.keys, [], 0)

      readable&.each do |io|
        if fiber = @readable.delete(io)
          fiber.resume
        end
      end

      writable&.each do |io|
        if fiber = @writable.delete(io)
          fiber.resume
        end
      end

      @waiting.keys.each do |fiber|
        if current_time > @waiting[fiber]
          @waiting.delete(fiber)
          fiber.resume
        end
      end

      ready, @ready = @ready, []
      ready.each do |fiber|
        fiber.resume
      end
    end
  end

  def io_wait(io, events, timeout)
    unless (events & IO::READABLE).zero?
      @readable[io] = Fiber.current
    end
    unless (events & IO::WRITABLE).zero?
      @writable[io] = Fiber.current
    end

    Fiber.yield
    return events
  end

  def kernel_sleep(duration = nil)
    block(:sleep, duration)
    return true
  end

  def block(blocker, timeout = nil)
    if timeout
      @waiting[Fiber.current] = current_time + timeout
      begin
        Fiber.yield
      ensure
        @waiting.delete(Fiber.current)
      end
    else
      @blocking += 1
      begin
        Fiber.yield
      ensure
        @blocking -= 1
      end
    end
  end

  def unblock(blocker, fiber)
    @ready << fiber
    io = @urgent.last
    io.write_nonblock('.')
  end

  def close
    run
    @urgent.each(&:close)
    @urgent = nil
  end

  private
  def current_time
    Process.clock_gettime(Process::CLOCK_MONOTONIC)
  end
end

scheduler = SimpleScheduler.new
Fiber.set_scheduler(scheduler)

puts "Go to sleep!"

f = Fiber.new(false) do
  puts "Going to sleep"
  sleep(1)
  puts "I slept well"
end

f.resume

puts "Wakey-wakey, sleepyhead"
```

Result:

```
Go to sleep!
Going to sleep
Wakey-wakey, sleepyhead
I slept well
```

When parameter is `true`:

```
require 'fiber'
require 'io/nonblock'

class SimpleScheduler
  def initialize
    @readable = {}
    @writable = {}
    @waiting = {}
    @ready = []
    @blocking = 0
    @urgent = IO.pipe
  end

  def run
    while @readable.any? or @writable.any? or @waiting.any? or @blocking.positive? or @ready.any?
      readable, writable = IO.select(@readable.keys + [@urgent.first], @writable.keys, [], 0)

      readable&.each do |io|
        if fiber = @readable.delete(io)
          fiber.resume
        end
      end

      writable&.each do |io|
        if fiber = @writable.delete(io)
          fiber.resume
        end
      end

      @waiting.keys.each do |fiber|
        if current_time > @waiting[fiber]
          @waiting.delete(fiber)
          fiber.resume
        end
      end

      ready, @ready = @ready, []
      ready.each do |fiber|
        fiber.resume
      end
    end
  end

  def io_wait(io, events, timeout)
    unless (events & IO::READABLE).zero?
      @readable[io] = Fiber.current
    end
    unless (events & IO::WRITABLE).zero?
      @writable[io] = Fiber.current
    end

    Fiber.yield
    return events
  end

  def kernel_sleep(duration = nil)
    block(:sleep, duration)
    return true
  end

  def block(blocker, timeout = nil)
    if timeout
      @waiting[Fiber.current] = current_time + timeout
      begin
        Fiber.yield
      ensure
        @waiting.delete(Fiber.current)
      end
    else
      @blocking += 1
      begin
        Fiber.yield
      ensure
        @blocking -= 1
      end
    end
  end

  def unblock(blocker, fiber)
    @ready << fiber
    io = @urgent.last
    io.write_nonblock('.')
  end

  def close
    run
    @urgent.each(&:close)
    @urgent = nil
  end

  private
  def current_time
    Process.clock_gettime(Process::CLOCK_MONOTONIC)
  end
end

scheduler = SimpleScheduler.new
Fiber.set_scheduler(scheduler)

puts "Go to sleep!"

f = Fiber.new(false) do
  puts "Going to sleep"
  sleep(1)
  puts "I slept well"
end

f.resume

puts "Wakey-wakey, sleepyhead"
```

Result (was the same):

```
Go to sleep!
Going to sleep
Wakey-wakey, sleepyhead
I slept well
```




-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:[e-mail]?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>