Change in vdsm[master]: rwlock: Replace misc.RWLock

Friday, 10 July 2015

Nir Soffer has uploaded a new change for review.

Change subject: rwlock: Replace misc.RWLock
......................................................................

rwlock: Replace misc.RWLock

This patch removes misc.RWLock and replace it with simpler
rwlock.RWLock.

The new lock does not support recursive locking or lock demotion, but I
think they are not used in by current code - not tested yet.

Change-Id: I9ae6064e8e031339303e64606a70673807c4083a
Signed-off-by: Nir Soffer <nsoffer(a)redhat.com&gt;
---
M vdsm/storage/misc.py
M vdsm/storage/resourceManager.py
2 files changed, 4 insertions(+), 112 deletions(-)


  git pull ssh://gerrit.ovirt.org:29418/vdsm refs/changes/23/43423/1

diff --git a/vdsm/storage/misc.py b/vdsm/storage/misc.py
index b14fd26..e45fad8 100644
--- a/vdsm/storage/misc.py
+++ b/vdsm/storage/misc.py
@@ -530,115 +530,6 @@
     return 0
 
 
-class RWLock(object):
-    """
-    A simple ReadWriteLock implementation.
-
-    The lock must be released by the thread that acquired it.  Once a thread
-    has acquired a lock, the same thread may acquire it again without blocking;
-    the thread must release it once for each time it has acquired it. Note that
-    lock promotion (acquiring an exclusive lock under a shared lock is
-    forbidden and will raise an exception.
-
-    The lock puts all requests in a queue. The request is granted when The
-    previous one is released.
-
-    Each request is represented by a :class:`threading.Event` object. When the
-    Event is set the request is granted. This enables multiple callers to wait
-    for a request thus implementing a shared lock.
-    """
-    class _contextLock(object):
-        def __init__(self, owner, exclusive):
-            self._owner = owner
-            self._exclusive = exclusive
-
-        def __enter__(self):
-            self._owner.acquire(self._exclusive)
-
-        def __exit__(self, exc_type, exc_value, traceback):
-            self._owner.release()
-
-    def __init__(self):
-        self._syncRoot = threading.Lock()
-        self._queue = Queue.Queue()
-        self._currentSharedLock = None
-        self._currentState = None
-        self._holdingThreads = {}
-
-        self.shared = self._contextLock(self, False)
-        self.exclusive = self._contextLock(self, True)
-
-    def acquireRead(self):
-        return self.acquire(False)
-
-    def acquireWrite(self):
-        return self.acquire(True)
-
-    def acquire(self, exclusive):
-        currentEvent = None
-        currentThread = threading.currentThread()
-
-        # Handle reacquiring lock in the same thread
-        if currentThread in self._holdingThreads:
-            if self._currentState is False and exclusive:
-                raise RuntimeError("Lock promotion is forbidden.")
-
-            self._holdingThreads[currentThread] += 1
-            return
-
-        with self._syncRoot:
-            # Handle regular acquisition
-            if exclusive:
-                currentEvent = threading.Event()
-                self._currentSharedLock = None
-            else:
-                if self._currentSharedLock is None:
-                    self._currentSharedLock = threading.Event()
-
-                currentEvent = self._currentSharedLock
-
-            try:
-                self._queue.put_nowait((currentEvent, exclusive))
-            except Queue.Full:
-                raise RuntimeError("There are too many objects waiting for "
-                                   "this lock")
-
-            if self._queue.unfinished_tasks == 1:
-                # Bootstrap the process if needed. A lock is released the when
-                # the next request is granted. When there is no one to grant
-                # the request you have to grant it yourself.
-                event, self._currentState = self._queue.get_nowait()
-                event.set()
-
-        currentEvent.wait()
-
-        self._holdingThreads[currentThread] = 0
-
-    def release(self):
-        currentThread = threading.currentThread()
-
-        if currentThread not in self._holdingThreads:
-            raise RuntimeError("Releasing an lock without acquiring it first")
-
-        # If in nested lock don't really release
-        if self._holdingThreads[currentThread] > 0:
-            self._holdingThreads[currentThread] -= 1
-            return
-
-        del self._holdingThreads[currentThread]
-
-        with self._syncRoot:
-            self._queue.task_done()
-
-            if self._queue.empty():
-                self._currentState = None
-                return
-
-            nextRequest, self._currentState = self._queue.get_nowait()
-
-        nextRequest.set()
-
-
 class DynamicBarrier(object):
     def __init__(self):
         self._cond = threading.Condition()
diff --git a/vdsm/storage/resourceManager.py b/vdsm/storage/resourceManager.py
index b1b0dc7..a7e67a2 100644
--- a/vdsm/storage/resourceManager.py
+++ b/vdsm/storage/resourceManager.py
@@ -29,6 +29,7 @@
 import storage_exception as se
 import misc
 from logUtils import SimpleLogAdapter
+from vdsm import rwlock
 from vdsm import utils
 
 
@@ -287,7 +288,7 @@
 
         self.autoRelease = True
         self._isValid = True
-        self._syncRoot = misc.RWLock()
+        self._syncRoot = rwlock.RWLock()
 
     def __wrapObj(self):
         for attr in dir(self.__wrappedObject):
@@ -380,11 +381,11 @@
         """
         def __init__(self, factory):
             self.resources = {}
-            self.lock = threading.Lock()  # misc.RWLock()
+            self.lock = threading.Lock()  # rwlock.RWLock()
             self.factory = factory
 
     def __init__(self):
-        self._syncRoot = misc.RWLock()
+        self._syncRoot = rwlock.RWLock()
         self._namespaces = {}
 
     @classmethod


-- 
To view, visit https://gerrit.ovirt.org/43423
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Gerrit-MessageType: newchange
Gerrit-Change-Id: I9ae6064e8e031339303e64606a70673807c4083a
Gerrit-PatchSet: 1
Gerrit-Project: vdsm
Gerrit-Branch: master
Gerrit-Owner: Nir Soffer <nsoffer(a)redhat.com&gt;

    

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