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Feature #18411
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Introduce `Fiber.blocking` for disabling scheduler.
Description
When implementing pure-ruby IO scheduler, we may need to invoke some Ruby IO operations without entering the scheduler.
def io_write(fiber, io, buffer, length)
offset = 0
while length > 0
# From offset until the end:
chunk = buffer.to_str(offset, length)
case result = io.write_nonblock(chunk, exception: false)
when :wait_readable
self.io_wait(fiber, io, IO::READABLE)
when :wait_writable
self.io_wait(fiber, io, IO::WRITABLE)
else
offset += result
length -= result
end
end
return offset
end
There are some cases where even in this code read_nonblock can invoke fiber scheduler creating infinite recursion.
Therefore, I propose to introduce Fiber.blocking{...} which has almost identical implementation to Fiber.new(blocking: true) {}.resume.
In the above code, we change the line:
case result = io.write_nonblock(chunk, exception: false)
to
case result = Fiber.blocking{io.write_nonblock(chunk, exception: false)}
This ensures that write_nonblock can never enter the scheduler again.
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