From e8242bd13de1f158cca48bb4f4a6f6bf56857f4a Mon Sep 17 00:00:00 2001
From: Ofer Koren <koreno@gmail.com>
Date: Mon, 22 Jun 2020 09:09:01 +0300
Subject: [PATCH] sync: allow specifying identity of reader when using RWLock

---
 easypy/sync.py       | 34 ++++++++++++++++++++++++++++------
 tests/test_rwlock.py | 28 +++++++++++++++++++++++++++-
 2 files changed, 55 insertions(+), 7 deletions(-)

diff --git a/easypy/sync.py b/easypy/sync.py
index 7ce85eaf..dc7bb129 100644
--- a/easypy/sync.py
+++ b/easypy/sync.py
@@ -684,7 +684,7 @@ def __init__(self, name=None):
         self._lease_timer = None
 
     def __repr__(self):
-        owners = ", ".join(map(str, sorted(self.owners.keys())))
+        owners = ", ".join(sorted(map(str, self.owners.keys())))
         lease_timer = self._lease_timer  # touch once to avoid races
         if lease_timer:
             mode = "exclusively ({})".format(lease_timer.elapsed)
@@ -700,25 +700,47 @@ def __call__(self):
         return self
 
     def __enter__(self):
+        self.acquire()
+        return self
+
+    def acquire(self, identifier=None):
+        """
+        Acquire the lock as a reader.
+        Optionally specify the identity of the reader (defaults to thready identity).
+        """
         while not self.cond.acquire(timeout=15):
             _logger.debug("%s - waiting...", self)
 
+        if not identifier:
+            identifier = _get_my_ident()
+
         try:
-            self.owners[_get_my_ident()] += 1
+            self.owners[identifier] += 1
             _verbose_logger.debug("%s - acquired (non-exclusively)", self)
             return self
         finally:
             self.cond.release()
 
     def __exit__(self, *args):
+        self.release()
+
+    def release(self, identifier=None):
+        """
+        Release the lock as a reader.
+        Optionally specify the identity of the reader (defaults to thready identity).
+        """
+
         while not self.cond.acquire(timeout=15):
             _logger.debug("%s - waiting...", self)
 
+        if not identifier:
+            identifier = _get_my_ident()
         try:
-            my_ident = _get_my_ident()
-            self.owners[my_ident] -= 1
-            if not self.owners[my_ident]:
-                self.owners.pop(my_ident)  # don't inflate the soft lock keys with threads that does not own it
+            if not self.owners[identifier]:
+                raise RuntimeError("cannot release un-acquired lock")
+            self.owners[identifier] -= 1
+            if not self.owners[identifier]:
+                self.owners.pop(identifier)
             self.cond.notify()
             _verbose_logger.debug("%s - released (non-exclusive)", self)
         finally:
diff --git a/tests/test_rwlock.py b/tests/test_rwlock.py
index 4ab12102..e7e0c069 100644
--- a/tests/test_rwlock.py
+++ b/tests/test_rwlock.py
@@ -1,5 +1,5 @@
 import threading
-
+import pytest
 import logging
 from easypy.concurrency import concurrent
 from easypy.sync import RWLock
@@ -76,3 +76,29 @@ def write():
         main_ctrl.clear()
         logging.info("write lock released")
         assert not state.reading and not state.writing
+
+
+def test_rwlock_different_threads():
+    lock = RWLock("test")
+    e = threading.Event()
+
+    def a(id=None):
+        lock.acquire(id)
+        e.wait()
+
+    def b(id=None):
+        lock.release(id)
+        e.set()
+
+    with concurrent(a):
+        assert lock.owners
+        with pytest.raises(RuntimeError):
+            b()
+        e.set()
+        assert lock.owners
+
+    with concurrent(a, "same"):
+        assert lock.owners
+        with concurrent(b, "same"):
+            pass
+        assert lock.owners