Hello python-dev,
This is probably worth of a bug report: While looking at threading.py I
noticed that Semaphore's counter can go below zero. This is opposed to
the docs: "The counter can never go below zero; ...". Just try:
import threading
s = threading.Semaphore(0.5)
# You can now acquire s as many times as you want!
# even when s._value < 0.
The fix is tiny:
diff -r 265d35e8fe82 Lib/threading.py
--- a/Lib/threading.py Fri Jan 27 21:17:04 2012 +0000
+++ b/Lib/threading.py Sat Jan 28 21:22:04 2012 +0200
@@ -322,7 +321,7 @@
rc = False
endtime = None
self._cond.acquire()
- while self._value == 0:
+ while self._value <= 0:
if not blocking:
break
if __debug__:
Which is better than forcing s._value to be an int.
I also think that the docs should be updated to reflect that the counter
is not compared to be equal to zero, but non-positive. e.g. "when
acquire() finds that it is zero...", "If it is zero on entry, block...".
On another commit: Regarding http://bugs.python.org/issue9346, an unused
import was left:
-from collections import deque
Cheers,
TB
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