3334130368
This fixes behavior in this situation: l1 <- lockShared Nothing "lck" l2 <- lockShared Nothing "lck" dropLock l1 dropLock l2 Before, the lock was dropped upon the second dropLock call, but the fd remained open, and would never be closed while the program was running. Fixed by a rather round-about method, but it should work well enough. It would have been simpler to open open the shared lock once, and not open it again in the second call to lockShared. But, that's difficult to do atomically. This also affects Windows and PID locks, not just posix locks. In the case of pid locks, multiple calls to waitLock within the same process are allowed because the side lock is locked using a posix lock, and so multiple exclusive locks can be taken in the same process. So, this change fixes a similar problem with pid locks. l1 <- waitLock (Seconds 1) "lck" l2 <- waitLock (Seconds 1) "lck" dropLock l1 dropLock l2 Here the l2 side lock fd remained open but not locked, although the pid lock file was removed. After this change, the second dropLock will close both fds to the side lock, and delete the pidlock.
34 lines
1 KiB
Haskell
34 lines
1 KiB
Haskell
{- Lock pool.
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-
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- This avoids a problem with unix fcntl locks: They are not composition-safe.
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-
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- For example, if one thread is holding a lock, and another thread opens the
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- lock file (to attempt to take or check the lock), and then closes it,
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- the lock will be released, despite the first thread still having the
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- lockfile open.
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-
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- Or, if a process is already holding an exclusive lock on a file, and
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- re-opens it and tries to take another exclusive lock, it won't block
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- on the first lock.
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-
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- To avoid these problems, this implements a lock pool. This keeps track
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- of which lock files are being used by the process, using STM to handle
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- inter-process locking.
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-
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- Note that, like Utility.LockFile, this does *not* attempt to be a
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- portability shim; the native locking of the OS is used.
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-
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- Copyright 2015 Joey Hess <id@joeyh.name>
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-
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- License: BSD-2-clause
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-}
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{-# LANGUAGE CPP #-}
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module Utility.LockPool (module X) where
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#ifndef mingw32_HOST_OS
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import Utility.LockPool.Posix as X
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#else
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import Utility.LockPool.Windows as X
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#endif
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