[ovirt-devel] [VDSM] [PATCH] Add the missing locked() interface

[Nir Soffer]

threading.Lock has a little known locked() method, documented in
https://docs.python.org/2.6/library/thread.html#thread.lock.locked

This method is not very useful, but since pthreading.Lock must be
drop-in replacment for threading.Lock, we must implement it.

This patch adds the missing method, implementing it in the same way
Python implemnts it.  Since RLock does not have this method, RLock does
not extend Lock now.

Signed-off-by: Nir Soffer <nsoffer at redhat.com>
---
 pthreading.py | 18 ++++++++++++++----
 tests.py      |  7 +++++++
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/pthreading.py b/pthreading.py
index 2e9e2d6..f1ea056 100644
--- a/pthreading.py
+++ b/pthreading.py
@@ -51,9 +51,9 @@ import os
 import pthread
 
 
-class Lock(pthread.Mutex):
+class _Lock(pthread.Mutex):
     """
-    Lock class mimics Python native threading.Lock() API on top of
+    _Lock class mimics Python native threading.Lock() API on top of
     the POSIX thread mutex synchronization primitive.
     """
     def __enter__(self):
@@ -78,9 +78,19 @@ class Lock(pthread.Mutex):
         self.unlock()
 
 
-class RLock(Lock):
+class Lock(_Lock):
+    def locked(self):
+        # Yes, this is horrible hack, and the same one used by Python
+        # threadmodule.c. But this is part of Python lock interface.
+        if self.acquire(blocking=False):
+            self.release()
+            return False
+        return True
+
+
+class RLock(_Lock):
     def __init__(self):
-        pthread.Mutex.__init__(self, recursive=True)
+        _Lock.__init__(self, recursive=True)
 
 
 class Condition(object):
diff --git a/tests.py b/tests.py
index d651288..f4c9746 100644
--- a/tests.py
+++ b/tests.py
@@ -60,6 +60,13 @@ class LockTests(TestCaseBase):
         self.assertTrue(lock.acquire())
         self.assertTrue(lock.acquire(False))
 
+    def testLocked(self):
+        lock = pthreading.Lock()
+        self.assertFalse(lock.locked())
+        with lock:
+            self.assertTrue(lock.locked())
+        self.assertFalse(lock.locked())
+
 
 class Flag(object):
     def __init__(self):
-- 
1.8.3.1