# pylint: disable-msg=W0613,W0201
import threading
+# Wouldn't it be better to define LockingError in the locking module?
+# Well, for now that's how the rest of the code does it...
+from ganeti import errors
+from ganeti import utils
+
+
+def ssynchronized(lock, shared=0):
+ """Shared Synchronization decorator.
+
+ Calls the function holding the given lock, either in exclusive or shared
+ mode. It requires the passed lock to be a SharedLock (or support its
+ semantics).
+
+ """
+ def wrap(fn):
+ def sync_function(*args, **kwargs):
+ lock.acquire(shared=shared)
+ try:
+ return fn(*args, **kwargs)
+ finally:
+ lock.release()
+ return sync_function
+ return wrap
class SharedLock:
# lock waiters
self.__nwait_exc = 0
self.__nwait_shr = 0
+ self.__npass_shr = 0
+
+ # is this lock in the deleted state?
+ self.__deleted = False
def __is_sharer(self):
"""Is the current thread sharing the lock at this time?"""
def _is_owned(self, shared=-1):
"""Is the current thread somehow owning the lock at this time?
- Args:
- shared:
- < 0: check for any type of ownership (default)
- 0: check for exclusive ownership
- > 0: check for shared ownership
+ @param shared:
+ - < 0: check for any type of ownership (default)
+ - 0: check for exclusive ownership
+ - > 0: check for shared ownership
"""
self.__lock.acquire()
try:
- result = self.__is_owned(shared)
+ result = self.__is_owned(shared=shared)
finally:
self.__lock.release()
return result
+ def __wait(self, c):
+ """Wait on the given condition, and raise an exception if the current lock
+ is declared deleted in the meantime.
+
+ @param c: the condition to wait on
+
+ """
+ c.wait()
+ if self.__deleted:
+ raise errors.LockError('deleted lock')
+
+ def __exclusive_acquire(self):
+ """Acquire the lock exclusively.
+
+ This is a private function that presumes you are already holding the
+ internal lock. It's defined separately to avoid code duplication between
+ acquire() and delete()
+
+ """
+ self.__nwait_exc += 1
+ try:
+ # This is to save ourselves from a nasty race condition that could
+ # theoretically make the sharers starve.
+ if self.__nwait_shr > 0 or self.__nwait_exc > 1:
+ self.__wait(self.__turn_exc)
+
+ while len(self.__shr) > 0 or self.__exc is not None:
+ self.__wait(self.__turn_exc)
+
+ self.__exc = threading.currentThread()
+ finally:
+ self.__nwait_exc -= 1
+
+ assert self.__npass_shr == 0, "SharedLock: internal fairness violation"
+
def acquire(self, blocking=1, shared=0):
"""Acquire a shared lock.
- Args:
- shared: whether to acquire in shared mode. By default an exclusive lock
- will be acquired.
- blocking: whether to block while trying to acquire or to operate in try-lock mode.
- this locking mode is not supported yet.
+ @param shared: whether to acquire in shared mode; by default an
+ exclusive lock will be acquired
+ @param blocking: whether to block while trying to acquire or to
+ operate in try-lock mode (this locking mode is not supported yet)
"""
if not blocking:
self.__lock.acquire()
try:
+ if self.__deleted:
+ raise errors.LockError('deleted lock')
+
# We cannot acquire the lock if we already have it
assert not self.__is_owned(), "double acquire() on a non-recursive lock"
+ assert self.__npass_shr >= 0, "Internal fairness condition weirdness"
if shared:
self.__nwait_shr += 1
try:
+ wait = False
# If there is an exclusive holder waiting we have to wait. We'll
# only do this once, though, when we start waiting for the lock. Then
# we'll just wait while there are no exclusive holders.
if self.__nwait_exc > 0:
# TODO: if !blocking...
- self.__turn_shr.wait()
+ wait = True
+ self.__wait(self.__turn_shr)
while self.__exc is not None:
+ wait = True
# TODO: if !blocking...
- self.__turn_shr.wait()
+ self.__wait(self.__turn_shr)
self.__shr.add(threading.currentThread())
+
+ # If we were waiting note that we passed
+ if wait:
+ self.__npass_shr -= 1
+
finally:
self.__nwait_shr -= 1
+ assert self.__npass_shr >= 0, "Internal fairness condition weirdness"
else:
- self.__nwait_exc += 1
- try:
- # This is to save ourselves from a nasty race condition that could
- # theoretically make the sharers starve.
- if self.__nwait_shr > 0 or self.__nwait_exc > 1:
- # TODO: if !blocking...
- self.__turn_exc.wait()
-
- while len(self.__shr) > 0 or self.__exc is not None:
- # TODO: if !blocking...
- self.__turn_exc.wait()
-
- self.__exc = threading.currentThread()
- finally:
- self.__nwait_exc -= 1
+ # TODO: if !blocking...
+ # (or modify __exclusive_acquire for non-blocking mode)
+ self.__exclusive_acquire()
finally:
self.__lock.release()
"""
self.__lock.acquire()
try:
+ assert self.__npass_shr >= 0, "Internal fairness condition weirdness"
# Autodetect release type
if self.__is_exclusive():
self.__exc = None
# mode if there are shared holders waiting. Otherwise wake up the next
# exclusive holder.
if self.__nwait_shr > 0:
+ # Make sure at least the ones which were blocked pass.
+ self.__npass_shr = self.__nwait_shr
self.__turn_shr.notifyAll()
elif self.__nwait_exc > 0:
- self.__turn_exc.notify()
+ self.__turn_exc.notify()
elif self.__is_sharer():
self.__shr.remove(threading.currentThread())
- # If there are shared holders waiting there *must* be an exclusive holder
- # waiting as well; otherwise what were they waiting for?
- assert (self.__nwait_shr == 0 or self.__nwait_exc > 0,
- "Lock sharers waiting while no exclusive is queueing")
-
- # If there are no more shared holders and some exclusive holders are
- # waiting let's wake one up.
- if len(self.__shr) == 0 and self.__nwait_exc > 0:
+ # If there are shared holders waiting (and not just scheduled to pass)
+ # there *must* be an exclusive holder waiting as well; otherwise what
+ # were they waiting for?
+ assert (self.__nwait_exc > 0 or self.__npass_shr == self.__nwait_shr), \
+ "Lock sharers waiting while no exclusive is queueing"
+
+ # If there are no more shared holders either in or scheduled to pass,
+ # and some exclusive holders are waiting let's wake one up.
+ if (len(self.__shr) == 0 and
+ self.__nwait_exc > 0 and
+ not self.__npass_shr > 0):
self.__turn_exc.notify()
else:
finally:
self.__lock.release()
+ def delete(self, blocking=1):
+ """Delete a Shared Lock.
+
+ This operation will declare the lock for removal. First the lock will be
+ acquired in exclusive mode if you don't already own it, then the lock
+ will be put in a state where any future and pending acquire() fail.
+
+ @param blocking: whether to block while trying to acquire or to
+ operate in try-lock mode. this locking mode is not supported
+ yet unless you are already holding exclusively the lock.
+
+ """
+ self.__lock.acquire()
+ try:
+ assert not self.__is_sharer(), "cannot delete() a lock while sharing it"
+
+ if self.__deleted:
+ raise errors.LockError('deleted lock')
+
+ if not self.__is_exclusive():
+ if not blocking:
+ # We don't have non-blocking mode for now
+ raise NotImplementedError
+ self.__exclusive_acquire()
+
+ self.__deleted = True
+ self.__exc = None
+ # Wake up everybody, they will fail acquiring the lock and
+ # raise an exception instead.
+ self.__turn_exc.notifyAll()
+ self.__turn_shr.notifyAll()
+
+ finally:
+ self.__lock.release()
+
+
+# Whenever we want to acquire a full LockSet we pass None as the value to acquire.
+# Hide this behing this nicely named constant.
+ALL_SET = None
+
+
+class LockSet:
+ """Implements a set of locks.
+
+ This abstraction implements a set of shared locks for the same resource type,
+ distinguished by name. The user can lock a subset of the resources and the
+ LockSet will take care of acquiring the locks always in the same order, thus
+ preventing deadlock.
+
+ All the locks needed in the same set must be acquired together, though.
+
+ """
+ def __init__(self, members=None):
+ """Constructs a new LockSet.
+
+ @param members: initial members of the set
+
+ """
+ # Used internally to guarantee coherency.
+ self.__lock = SharedLock()
+
+ # The lockdict indexes the relationship name -> lock
+ # The order-of-locking is implied by the alphabetical order of names
+ self.__lockdict = {}
+
+ if members is not None:
+ for name in members:
+ self.__lockdict[name] = SharedLock()
+
+ # The owner dict contains the set of locks each thread owns. For
+ # performance each thread can access its own key without a global lock on
+ # this structure. It is paramount though that *no* other type of access is
+ # done to this structure (eg. no looping over its keys). *_owner helper
+ # function are defined to guarantee access is correct, but in general never
+ # do anything different than __owners[threading.currentThread()], or there
+ # will be trouble.
+ self.__owners = {}
+
+ def _is_owned(self):
+ """Is the current thread a current level owner?"""
+ return threading.currentThread() in self.__owners
+
+ def _add_owned(self, name=None):
+ """Note the current thread owns the given lock"""
+ if name is None:
+ if not self._is_owned():
+ self.__owners[threading.currentThread()] = set()
+ else:
+ if self._is_owned():
+ self.__owners[threading.currentThread()].add(name)
+ else:
+ self.__owners[threading.currentThread()] = set([name])
+
+
+ def _del_owned(self, name=None):
+ """Note the current thread owns the given lock"""
+
+ if name is not None:
+ self.__owners[threading.currentThread()].remove(name)
+
+ # Only remove the key if we don't hold the set-lock as well
+ if (not self.__lock._is_owned() and
+ not self.__owners[threading.currentThread()]):
+ del self.__owners[threading.currentThread()]
+
+ def _list_owned(self):
+ """Get the set of resource names owned by the current thread"""
+ if self._is_owned():
+ return self.__owners[threading.currentThread()].copy()
+ else:
+ return set()
+
+ def __names(self):
+ """Return the current set of names.
+
+ Only call this function while holding __lock and don't iterate on the
+ result after releasing the lock.
+
+ """
+ return self.__lockdict.keys()
+
+ def _names(self):
+ """Return a copy of the current set of elements.
+
+ Used only for debugging purposes.
+
+ """
+ # If we don't already own the set-level lock acquired
+ # we'll get it and note we need to release it later.
+ release_lock = False
+ if not self.__lock._is_owned():
+ release_lock = True
+ self.__lock.acquire(shared=1)
+ try:
+ result = self.__names()
+ finally:
+ if release_lock:
+ self.__lock.release()
+ return set(result)
+
+ def acquire(self, names, blocking=1, shared=0):
+ """Acquire a set of resource locks.
+
+ @param names: the names of the locks which shall be acquired
+ (special lock names, or instance/node names)
+ @param shared: whether to acquire in shared mode; by default an
+ exclusive lock will be acquired
+ @param blocking: whether to block while trying to acquire or to
+ operate in try-lock mode (this locking mode is not supported yet)
+
+ @return: True when all the locks are successfully acquired
+
+ @raise errors.LockError: when any lock we try to acquire has
+ been deleted before we succeed. In this case none of the
+ locks requested will be acquired.
+
+ """
+ if not blocking:
+ # We don't have non-blocking mode for now
+ raise NotImplementedError
+
+ # Check we don't already own locks at this level
+ assert not self._is_owned(), "Cannot acquire locks in the same set twice"
+
+ if names is None:
+ # If no names are given acquire the whole set by not letting new names
+ # being added before we release, and getting the current list of names.
+ # Some of them may then be deleted later, but we'll cope with this.
+ #
+ # We'd like to acquire this lock in a shared way, as it's nice if
+ # everybody else can use the instances at the same time. If are acquiring
+ # them exclusively though they won't be able to do this anyway, though,
+ # so we'll get the list lock exclusively as well in order to be able to
+ # do add() on the set while owning it.
+ self.__lock.acquire(shared=shared)
+ try:
+ # note we own the set-lock
+ self._add_owned()
+ names = self.__names()
+ except:
+ # We shouldn't have problems adding the lock to the owners list, but
+ # if we did we'll try to release this lock and re-raise exception.
+ # Of course something is going to be really wrong, after this.
+ self.__lock.release()
+ raise
+
+ try:
+ # Support passing in a single resource to acquire rather than many
+ if isinstance(names, basestring):
+ names = [names]
+ else:
+ names.sort()
+
+ acquire_list = []
+ # First we look the locks up on __lockdict. We have no way of being sure
+ # they will still be there after, but this makes it a lot faster should
+ # just one of them be the already wrong
+ for lname in utils.UniqueSequence(names):
+ try:
+ lock = self.__lockdict[lname] # raises KeyError if lock is not there
+ acquire_list.append((lname, lock))
+ except (KeyError):
+ if self.__lock._is_owned():
+ # We are acquiring all the set, it doesn't matter if this particular
+ # element is not there anymore.
+ continue
+ else:
+ raise errors.LockError('non-existing lock in set (%s)' % lname)
+
+ # This will hold the locknames we effectively acquired.
+ acquired = set()
+ # Now acquire_list contains a sorted list of resources and locks we want.
+ # In order to get them we loop on this (private) list and acquire() them.
+ # We gave no real guarantee they will still exist till this is done but
+ # .acquire() itself is safe and will alert us if the lock gets deleted.
+ for (lname, lock) in acquire_list:
+ try:
+ lock.acquire(shared=shared) # raises LockError if the lock is deleted
+ # now the lock cannot be deleted, we have it!
+ self._add_owned(name=lname)
+ acquired.add(lname)
+ except (errors.LockError):
+ if self.__lock._is_owned():
+ # We are acquiring all the set, it doesn't matter if this particular
+ # element is not there anymore.
+ continue
+ else:
+ name_fail = lname
+ for lname in self._list_owned():
+ self.__lockdict[lname].release()
+ self._del_owned(name=lname)
+ raise errors.LockError('non-existing lock in set (%s)' % name_fail)
+ except:
+ # We shouldn't have problems adding the lock to the owners list, but
+ # if we did we'll try to release this lock and re-raise exception.
+ # Of course something is going to be really wrong, after this.
+ if lock._is_owned():
+ lock.release()
+ raise
+
+ except:
+ # If something went wrong and we had the set-lock let's release it...
+ if self.__lock._is_owned():
+ self.__lock.release()
+ raise
+
+ return acquired
+
+ def release(self, names=None):
+ """Release a set of resource locks, at the same level.
+
+ You must have acquired the locks, either in shared or in exclusive mode,
+ before releasing them.
+
+ @param names: the names of the locks which shall be released
+ (defaults to all the locks acquired at that level).
+
+ """
+ assert self._is_owned(), "release() on lock set while not owner"
+
+ # Support passing in a single resource to release rather than many
+ if isinstance(names, basestring):
+ names = [names]
+
+ if names is None:
+ names = self._list_owned()
+ else:
+ names = set(names)
+ assert self._list_owned().issuperset(names), (
+ "release() on unheld resources %s" %
+ names.difference(self._list_owned()))
+
+ # First of all let's release the "all elements" lock, if set.
+ # After this 'add' can work again
+ if self.__lock._is_owned():
+ self.__lock.release()
+ self._del_owned()
+
+ for lockname in names:
+ # If we are sure the lock doesn't leave __lockdict without being
+ # exclusively held we can do this...
+ self.__lockdict[lockname].release()
+ self._del_owned(name=lockname)
+
+ def add(self, names, acquired=0, shared=0):
+ """Add a new set of elements to the set
+
+ @param names: names of the new elements to add
+ @param acquired: pre-acquire the new resource?
+ @param shared: is the pre-acquisition shared?
+
+ """
+ # Check we don't already own locks at this level
+ assert not self._is_owned() or self.__lock._is_owned(shared=0), \
+ "Cannot add locks if the set is only partially owned, or shared"
+
+ # Support passing in a single resource to add rather than many
+ if isinstance(names, basestring):
+ names = [names]
+
+ # If we don't already own the set-level lock acquired in an exclusive way
+ # we'll get it and note we need to release it later.
+ release_lock = False
+ if not self.__lock._is_owned():
+ release_lock = True
+ self.__lock.acquire()
+
+ try:
+ invalid_names = set(self.__names()).intersection(names)
+ if invalid_names:
+ # This must be an explicit raise, not an assert, because assert is
+ # turned off when using optimization, and this can happen because of
+ # concurrency even if the user doesn't want it.
+ raise errors.LockError("duplicate add() (%s)" % invalid_names)
+
+ for lockname in names:
+ lock = SharedLock()
+
+ if acquired:
+ lock.acquire(shared=shared)
+ # now the lock cannot be deleted, we have it!
+ try:
+ self._add_owned(name=lockname)
+ except:
+ # We shouldn't have problems adding the lock to the owners list,
+ # but if we did we'll try to release this lock and re-raise
+ # exception. Of course something is going to be really wrong,
+ # after this. On the other hand the lock hasn't been added to the
+ # __lockdict yet so no other threads should be pending on it. This
+ # release is just a safety measure.
+ lock.release()
+ raise
+
+ self.__lockdict[lockname] = lock
+
+ finally:
+ # Only release __lock if we were not holding it previously.
+ if release_lock:
+ self.__lock.release()
+
+ return True
+
+ def remove(self, names, blocking=1):
+ """Remove elements from the lock set.
+
+ You can either not hold anything in the lockset or already hold a superset
+ of the elements you want to delete, exclusively.
+
+ @param names: names of the resource to remove.
+ @param blocking: whether to block while trying to acquire or to
+ operate in try-lock mode (this locking mode is not supported
+ yet unless you are already holding exclusively the locks)
+
+ @return:: a list of locks which we removed; the list is always
+ equal to the names list if we were holding all the locks
+ exclusively
+
+ """
+ if not blocking and not self._is_owned():
+ # We don't have non-blocking mode for now
+ raise NotImplementedError
+
+ # Support passing in a single resource to remove rather than many
+ if isinstance(names, basestring):
+ names = [names]
+
+ # If we own any subset of this lock it must be a superset of what we want
+ # to delete. The ownership must also be exclusive, but that will be checked
+ # by the lock itself.
+ assert not self._is_owned() or self._list_owned().issuperset(names), (
+ "remove() on acquired lockset while not owning all elements")
+
+ removed = []
+
+ for lname in names:
+ # Calling delete() acquires the lock exclusively if we don't already own
+ # it, and causes all pending and subsequent lock acquires to fail. It's
+ # fine to call it out of order because delete() also implies release(),
+ # and the assertion above guarantees that if we either already hold
+ # everything we want to delete, or we hold none.
+ try:
+ self.__lockdict[lname].delete()
+ removed.append(lname)
+ except (KeyError, errors.LockError):
+ # This cannot happen if we were already holding it, verify:
+ assert not self._is_owned(), "remove failed while holding lockset"
+ else:
+ # If no LockError was raised we are the ones who deleted the lock.
+ # This means we can safely remove it from lockdict, as any further or
+ # pending delete() or acquire() will fail (and nobody can have the lock
+ # since before our call to delete()).
+ #
+ # This is done in an else clause because if the exception was thrown
+ # it's the job of the one who actually deleted it.
+ del self.__lockdict[lname]
+ # And let's remove it from our private list if we owned it.
+ if self._is_owned():
+ self._del_owned(name=lname)
+
+ return removed
+
+
+# Locking levels, must be acquired in increasing order.
+# Current rules are:
+# - at level LEVEL_CLUSTER resides the Big Ganeti Lock (BGL) which must be
+# acquired before performing any operation, either in shared or in exclusive
+# mode. acquiring the BGL in exclusive mode is discouraged and should be
+# avoided.
+# - at levels LEVEL_NODE and LEVEL_INSTANCE reside node and instance locks.
+# If you need more than one node, or more than one instance, acquire them at
+# the same time.
+LEVEL_CLUSTER = 0
+LEVEL_INSTANCE = 1
+LEVEL_NODE = 2
+
+LEVELS = [LEVEL_CLUSTER,
+ LEVEL_INSTANCE,
+ LEVEL_NODE]
+
+# Lock levels which are modifiable
+LEVELS_MOD = [LEVEL_NODE, LEVEL_INSTANCE]
+
+# Constant for the big ganeti lock
+BGL = 'BGL'
+
+
+class GanetiLockManager:
+ """The Ganeti Locking Library
+
+ The purpouse of this small library is to manage locking for ganeti clusters
+ in a central place, while at the same time doing dynamic checks against
+ possible deadlocks. It will also make it easier to transition to a different
+ lock type should we migrate away from python threads.
+
+ """
+ _instance = None
+
+ def __init__(self, nodes=None, instances=None):
+ """Constructs a new GanetiLockManager object.
+
+ There should be only a GanetiLockManager object at any time, so this
+ function raises an error if this is not the case.
+
+ @param nodes: list of node names
+ @param instances: list of instance names
+
+ """
+ assert self.__class__._instance is None, \
+ "double GanetiLockManager instance"
+
+ self.__class__._instance = self
+
+ # The keyring contains all the locks, at their level and in the correct
+ # locking order.
+ self.__keyring = {
+ LEVEL_CLUSTER: LockSet([BGL]),
+ LEVEL_NODE: LockSet(nodes),
+ LEVEL_INSTANCE: LockSet(instances),
+ }
+
+ def _names(self, level):
+ """List the lock names at the given level.
+
+ This can be used for debugging/testing purposes.
+
+ @param level: the level whose list of locks to get
+
+ """
+ assert level in LEVELS, "Invalid locking level %s" % level
+ return self.__keyring[level]._names()
+
+ def _is_owned(self, level):
+ """Check whether we are owning locks at the given level
+
+ """
+ return self.__keyring[level]._is_owned()
+
+ is_owned = _is_owned
+
+ def _list_owned(self, level):
+ """Get the set of owned locks at the given level
+
+ """
+ return self.__keyring[level]._list_owned()
+
+ def _upper_owned(self, level):
+ """Check that we don't own any lock at a level greater than the given one.
+
+ """
+ # This way of checking only works if LEVELS[i] = i, which we check for in
+ # the test cases.
+ return utils.any((self._is_owned(l) for l in LEVELS[level + 1:]))
+
+ def _BGL_owned(self):
+ """Check if the current thread owns the BGL.
+
+ Both an exclusive or a shared acquisition work.
+
+ """
+ return BGL in self.__keyring[LEVEL_CLUSTER]._list_owned()
+
+ def _contains_BGL(self, level, names):
+ """Check if the level contains the BGL.
+
+ Check if acting on the given level and set of names will change
+ the status of the Big Ganeti Lock.
+
+ """
+ return level == LEVEL_CLUSTER and (names is None or BGL in names)
+
+ def acquire(self, level, names, blocking=1, shared=0):
+ """Acquire a set of resource locks, at the same level.
+
+ @param level: the level at which the locks shall be acquired;
+ it must be a memmber of LEVELS.
+ @param names: the names of the locks which shall be acquired
+ (special lock names, or instance/node names)
+ @param shared: whether to acquire in shared mode; by default
+ an exclusive lock will be acquired
+ @param blocking: whether to block while trying to acquire or to
+ operate in try-lock mode (this locking mode is not supported yet)
+
+ """
+ assert level in LEVELS, "Invalid locking level %s" % level
+
+ # Check that we are either acquiring the Big Ganeti Lock or we already own
+ # it. Some "legacy" opcodes need to be sure they are run non-concurrently
+ # so even if we've migrated we need to at least share the BGL to be
+ # compatible with them. Of course if we own the BGL exclusively there's no
+ # point in acquiring any other lock, unless perhaps we are half way through
+ # the migration of the current opcode.
+ assert (self._contains_BGL(level, names) or self._BGL_owned()), (
+ "You must own the Big Ganeti Lock before acquiring any other")
+
+ # Check we don't own locks at the same or upper levels.
+ assert not self._upper_owned(level), ("Cannot acquire locks at a level"
+ " while owning some at a greater one")
+
+ # Acquire the locks in the set.
+ return self.__keyring[level].acquire(names, shared=shared,
+ blocking=blocking)
+
+ def release(self, level, names=None):
+ """Release a set of resource locks, at the same level.
+
+ You must have acquired the locks, either in shared or in exclusive
+ mode, before releasing them.
+
+ @param level: the level at which the locks shall be released;
+ it must be a memmber of LEVELS
+ @param names: the names of the locks which shall be released
+ (defaults to all the locks acquired at that level)
+
+ """
+ assert level in LEVELS, "Invalid locking level %s" % level
+ assert (not self._contains_BGL(level, names) or
+ not self._upper_owned(LEVEL_CLUSTER)), (
+ "Cannot release the Big Ganeti Lock while holding something"
+ " at upper levels")
+
+ # Release will complain if we don't own the locks already
+ return self.__keyring[level].release(names)
+
+ def add(self, level, names, acquired=0, shared=0):
+ """Add locks at the specified level.
+
+ @param level: the level at which the locks shall be added;
+ it must be a memmber of LEVELS_MOD.
+ @param names: names of the locks to acquire
+ @param acquired: whether to acquire the newly added locks
+ @param shared: whether the acquisition will be shared
+
+ """
+ assert level in LEVELS_MOD, "Invalid or immutable level %s" % level
+ assert self._BGL_owned(), ("You must own the BGL before performing other"
+ " operations")
+ assert not self._upper_owned(level), ("Cannot add locks at a level"
+ " while owning some at a greater one")
+ return self.__keyring[level].add(names, acquired=acquired, shared=shared)
+
+ def remove(self, level, names, blocking=1):
+ """Remove locks from the specified level.
+
+ You must either already own the locks you are trying to remove
+ exclusively or not own any lock at an upper level.
+
+ @param level: the level at which the locks shall be removed;
+ it must be a member of LEVELS_MOD
+ @param names: the names of the locks which shall be removed
+ (special lock names, or instance/node names)
+ @param blocking: whether to block while trying to operate in
+ try-lock mode (this locking mode is not supported yet)
+
+ """
+ assert level in LEVELS_MOD, "Invalid or immutable level %s" % level
+ assert self._BGL_owned(), ("You must own the BGL before performing other"
+ " operations")
+ # Check we either own the level or don't own anything from here up.
+ # LockSet.remove() will check the case in which we don't own all the needed
+ # resources, or we have a shared ownership.
+ assert self._is_owned(level) or not self._upper_owned(level), (
+ "Cannot remove locks at a level while not owning it or"
+ " owning some at a greater one")
+ return self.__keyring[level].remove(names, blocking=blocking)
projects / ganeti-local / blobdiff