[Python-checkins] gh-97545: Make Semaphore run faster. (#97549)

Mon Sep 26 19:38:09 EDT 2022

https://github.com/python/cpython/commit/68c46ae68b6e0c36a12e37285fff9ce0782ed01e
commit: 68c46ae68b6e0c36a12e37285fff9ce0782ed01e
branch: main
author: Cyker Way <cykerway at gmail.com>
committer: gvanrossum <gvanrossum at gmail.com>
date: 2022年09月26日T16:38:00-07:00
summary:
gh-97545: Make Semaphore run faster. (#97549)
files:
A Misc/NEWS.d/next/Library/2022-09-25-23-24-52.gh-issue-97545.HZLSNt.rst
M Lib/asyncio/locks.py
M Lib/test/test_asyncio/test_locks.py

diff --git a/Lib/asyncio/locks.py b/Lib/asyncio/locks.py
index e86d11deb476..ce5d8d5bfb2e 100644
--- a/Lib/asyncio/locks.py
+++ b/Lib/asyncio/locks.py
@@ -356,8 +356,9 @@ def __repr__(self):
 return f'<{res[1:-1]} [{extra}]>'
 
 def locked(self):
- """Returns True if semaphore counter is zero."""
- return self._value == 0
+ """Returns True if semaphore cannot be acquired immediately."""
+ return self._value == 0 or (
+ any(not w.cancelled() for w in (self._waiters or ())))
 
 async def acquire(self):
 """Acquire a semaphore.
@@ -368,8 +369,7 @@ async def acquire(self):
 called release() to make it larger than 0, and then return
 True.
 """
- if (not self.locked() and (self._waiters is None or
- all(w.cancelled() for w in self._waiters))):
+ if not self.locked():
 self._value -= 1
 return True
 
@@ -387,13 +387,13 @@ async def acquire(self):
 finally:
 self._waiters.remove(fut)
 except exceptions.CancelledError:
- if not self.locked():
- self._wake_up_first()
+ if not fut.cancelled():
+ self._value += 1
+ self._wake_up_next()
 raise
 
- self._value -= 1
- if not self.locked():
- self._wake_up_first()
+ if self._value > 0:
+ self._wake_up_next()
 return True
 
 def release(self):
@@ -403,22 +403,18 @@ def release(self):
 become larger than zero again, wake up that coroutine.
 """
 self._value += 1
- self._wake_up_first()
+ self._wake_up_next()
 
- def _wake_up_first(self):
- """Wake up the first waiter if it isn't done."""
+ def _wake_up_next(self):
+ """Wake up the first waiter that isn't done."""
 if not self._waiters:
 return
- try:
- fut = next(iter(self._waiters))
- except StopIteration:
- return
 
- # .done() necessarily means that a waiter will wake up later on and
- # either take the lock, or, if it was cancelled and lock wasn't
- # taken already, will hit this again and wake up a new waiter.
- if not fut.done():
- fut.set_result(True)
+ for fut in self._waiters:
+ if not fut.done():
+ self._value -= 1
+ fut.set_result(True)
+ return
 
 
 class BoundedSemaphore(Semaphore):
diff --git a/Lib/test/test_asyncio/test_locks.py b/Lib/test/test_asyncio/test_locks.py
index 1eb25e787576..f6c6a282429a 100644
--- a/Lib/test/test_asyncio/test_locks.py
+++ b/Lib/test/test_asyncio/test_locks.py
@@ -844,9 +844,8 @@ async def c4(result):
 
 sem.release()
 sem.release()
- self.assertEqual(2, sem._value)
+ self.assertEqual(0, sem._value)
 
- await asyncio.sleep(0)
 await asyncio.sleep(0)
 self.assertEqual(0, sem._value)
 self.assertEqual(3, len(result))
diff --git a/Misc/NEWS.d/next/Library/2022-09-25-23-24-52.gh-issue-97545.HZLSNt.rst b/Misc/NEWS.d/next/Library/2022-09-25-23-24-52.gh-issue-97545.HZLSNt.rst
new file mode 100644
index 000000000000..a53902ea670b
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-09-25-23-24-52.gh-issue-97545.HZLSNt.rst
@@ -0,0 +1 @@
+Make Semaphore run faster.
