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plurals

PO
primarykey
Id
2774079
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
2
CommunityOwnedDate
CreationDate
2010-05-05T14:27:14.220
FavoriteCount
0
LastActivityDate
2010-05-05T14:33:32.483
LastEditDate
2010-05-05T14:33:32.483
LastEditorUserId
95810
OwnerUserId
95810
ParentId
2773935
PostTypeId
2
Score
7
ViewCount
0
LastEditorDisplayName
text
Body
In the general case, a single global lock is less efficient (more contention) but safer (no risk of deadlock) as long as it's a <code>RLock</code> (reentrant) rather than a plain <code>Lock</code>. The potential problems come when a thread that's executing while holding a lock tries to acquire another (or the same) lock, for example by calling another method that contains the <code>acquire</code> call. If a thread that's already holding a lock tries to acquire it again, it will block forever if the lock's a plain <code>Lock</code>, but proceed smoothly if it's a slightly more complex <code>RLock</code> -- that's why the latter is called reentrant, because the thread holding it can "enter" (acquire the lock) again. Essentially, a RLock keeps track of which thread holds it, and how many time the thread has acquired the lock, while the simpler Lock does not keep such information around. With multiple locks, the deadlock problem comes when one thread tries to acquire lock A then lock B, while another tries to acquire first lock B, then lock A. If that occurs, then sooner or later you'll be in a situation where the first lock holds A, the second one holds B, and each tries to acquire the lock that the other one is holding -- so both block forever. One way to prevent multiple-lock deadlocks is to make sure that locks are always acquired in the same order, whatever thread is doing the acquiring. However, when each instance has its own lock, that's exceedingly difficult to organize with any clarity and simplicity.
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Title
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1. This table or related slice is empty.
PostParentId
1. POPython Locking Implementation (with threading module)
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 PTQuestion
PostTypePostTypeId
1. PTAnswer
UserLastEditorUserId
1. USAlex Martelli
UserOwnerUserId
1. USAlex Martelli
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1. VO
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 VTUpMod
2. VO
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3. VO
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CommentsPostId
1. COofftopic Congrats for your 100k !!! ..
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 USOscarRyz
2. CO@Oscar, thanks!-)
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 USAlex Martelli

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