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Diffstat (limited to 'libpod/lock/lock.go')
| -rw-r--r-- | libpod/lock/lock.go | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/libpod/lock/lock.go b/libpod/lock/lock.go new file mode 100644 index 000000000..73c1fdcf7 --- /dev/null +++ b/libpod/lock/lock.go @@ -0,0 +1,58 @@ +package lock + +// Manager provides an interface for allocating multiprocess locks. +// Locks returned by Manager MUST be multiprocess - allocating a lock in +// process A and retrieving that lock's ID in process B must return handles for +// the same lock, and locking the lock in A should exclude B from the lock until +// it is unlocked in A. +// All locks must be identified by a UUID (retrieved with Locker's ID() method). +// All locks with a given UUID must refer to the same underlying lock, and it +// must be possible to retrieve the lock given its UUID. +// Each UUID should refer to a unique underlying lock. +// Calls to AllocateLock() must return a unique, unallocated UUID. +// AllocateLock() must fail once all available locks have been allocated. +// Locks are returned to use by calls to Free(), and can subsequently be +// reallocated. +type Manager interface { + // AllocateLock returns an unallocated lock. + // It is guaranteed that the same lock will not be returned again by + // AllocateLock until the returned lock has Free() called on it. + // If all available locks are allocated, AllocateLock will return an + // error. + AllocateLock() (Locker, error) + // RetrieveLock retrieves a lock given its UUID. + // The underlying lock MUST be the same as another other lock with the + // same UUID. + RetrieveLock(id uint32) (Locker, error) +} + +// Locker is similar to sync.Locker, but provides a method for freeing the lock +// to allow its reuse. +// All Locker implementations must maintain mutex semantics - the lock only +// allows one caller in the critical section at a time. +// All locks with the same ID must refer to the same underlying lock, even +// if they are within multiple processes. +type Locker interface { + // ID retrieves the lock's ID. + // ID is guaranteed to uniquely identify the lock within the + // Manager - that is, calling RetrieveLock with this ID will return + // another instance of the same lock. + ID() uint32 + // Lock locks the lock. + // This call MUST block until it successfully acquires the lock or + // encounters a fatal error. + // All errors must be handled internally, as they are not returned. For + // the most part, panicking should be appropriate. + Lock() + // Unlock unlocks the lock. + // All errors must be handled internally, as they are not returned. For + // the most part, panicking should be appropriate. + // This includes unlocking locks which are already unlocked. + Unlock() + // Free deallocates the underlying lock, allowing its reuse by other + // pods and containers. + // The lock MUST still be usable after a Free() - some libpod instances + // may still retain Container structs with the old lock. This simply + // advises the manager that the lock may be reallocated. + Free() error +} |