concurrent.interpreters.Queue.get()/put() mishandle the timeout argument

[tonghuaroot]

concurrent.interpreters.Queue.get() and Queue.put() mishandle their
timeout argument in three related ways.

1. The value is converted with int(timeout), which truncates a floating-point
   timeout to whole seconds. A timeout in the interval [0, 1) becomes a
   non-blocking call, and e.g. timeout=1.9 waits for only about one second.
   queue.Queue, which this queue is meant to be compatible with, accepts a
   floating-point number of seconds.

2. Because of the same int() conversion, a small negative float such as
   timeout=-0.5 is truncated to 0 and passes the timeout < 0 check
   instead of raising ValueError.

3. The deadline is computed with time.time() (the wall clock), while
   queue.Queue uses time.monotonic(). The timeout can therefore over- or
   under-wait if the system clock is adjusted (NTP step, manual change) during
   the call.

Reproducer (3.14.5)

import time
from concurrent.interpreters import create_queue

q = create_queue(maxsize=1)
q.put(b"x")                      # fill it
start = time.perf_counter()
try:
    q.put(b"y", timeout=0.5)     # expected: block ~0.5s, then QueueFull
except Exception as exc:
    print(type(exc).__name__, f"{(time.perf_counter() - start) * 1000:.1f} ms")
# -> QueueFull 0.0 ms   (expected ~500 ms)

q2 = create_queue()
start = time.perf_counter()
try:
    q2.get(timeout=0.9)          # expected: block ~0.9s, then QueueEmpty
except Exception as exc:
    print(type(exc).__name__, f"{(time.perf_counter() - start) * 1000:.1f} ms")
# -> QueueEmpty 0.0 ms  (expected ~900 ms)

For comparison, queue.Queue().get(timeout=0.5) blocks for about 500 ms.

The fix is to use the timeout value as given, reject a negative or NaN timeout
with ValueError, and base the deadline on time.monotonic().

Linked PRs

• gh-153005: Fix timeout handling in concurrent.interpreters.Queue #153006