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Prevent deadlock in IMAPServer.close when using 'maxsyncaccounts' and 'maxconnections'. #241

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Prevent deadlock in IMAPServer.close when using 'maxsyncaccounts' and 'maxconnections'. #241

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20 changes: 15 additions & 5 deletions offlineimap/imapserver.py
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Original file line number Diff line number Diff line change
Expand Up @@ -158,6 +158,7 @@ def __init__(self, repos):
self.lastowner = {}
self.semaphore = BoundedSemaphore(self.maxconnections)
self.connectionlock = Lock()
self.closing = False
self.reference = repos.getreference()
self.idlefolders = repos.getidlefolders()
self.gss_vc = None
Expand Down Expand Up @@ -569,6 +570,11 @@ def acquireconnection(self):

self.semaphore.acquire()
self.connectionlock.acquire()
if self.closing:
self.connectionlock.release()
self.semaphore.release()
raise OfflineImapError("Server is closing",
OfflineImapError.ERROR.REPO)
curThread = current_thread()
imapobj = None

Expand Down Expand Up @@ -793,14 +799,17 @@ def connectionwait(self):
self.semaphore.release()

def close(self):
# First make sure no new connections can be established.
self.connectionlock.acquire()
self.closing = True
self.connectionlock.release()

# Make sure I own all the semaphores. Let the threads finish
# their stuff. This is a blocking method.
# Make sure to not call this under connectionlock to avoid deadlocks.
threadutil.semaphorereset(self.semaphore, self.maxconnections)

with self.connectionlock:
# first, wait till all connections had been released.
# TODO: won't work IMHO, as releaseconnection() also
# requires the connectionlock, leading to a potential
# deadlock! Audit & check!
threadutil.semaphorereset(self.semaphore, self.maxconnections)
for imapobj in self.assignedconnections + self.availableconnections:
imapobj.logout()
self.assignedconnections = []
Expand All @@ -809,6 +818,7 @@ def close(self):
# reset GSSAPI state
self.gss_vc = None
self.gssapi = False
self.closing = False

def keepalive(self, timeout, event):
"""Sends a NOOP to each connection recorded.
Expand Down