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d2b77f8b33
The original intent behind the requirement was to ensure that, if two SHM lock structs were open at the same time, we should not make such a runtime available to the user, and should clean it up instead. It turns out that we don't even need to open a second SHM lock struct - if we get an error mapping the first one due to a lock count mismatch, we can just delete it, and it cleans itself up when it errors. So there's no reason not to return a valid runtime. Signed-off-by: Matthew Heon <matthew.heon@pm.me>
103 lines
2.2 KiB
Go
103 lines
2.2 KiB
Go
package lock
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import (
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"sync"
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"github.com/pkg/errors"
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)
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// Mutex holds a single mutex and whether it has been allocated.
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type Mutex struct {
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id uint32
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lock sync.Mutex
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allocated bool
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}
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// ID retrieves the ID of the mutex
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func (m *Mutex) ID() uint32 {
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return m.id
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}
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// Lock locks the mutex
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func (m *Mutex) Lock() {
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m.lock.Lock()
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}
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// Unlock unlocks the mutex
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func (m *Mutex) Unlock() {
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m.lock.Unlock()
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}
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// Free deallocates the mutex to allow its reuse
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func (m *Mutex) Free() error {
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m.allocated = false
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return nil
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}
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// InMemoryManager is a lock manager that allocates and retrieves local-only
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// locks - that is, they are not multiprocess. This lock manager is intended
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// purely for unit and integration testing and should not be used in production
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// deployments.
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type InMemoryManager struct {
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locks []*Mutex
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numLocks uint32
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localLock sync.Mutex
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}
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// NewInMemoryManager creates a new in-memory lock manager with the given number
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// of locks.
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func NewInMemoryManager(numLocks uint32) (Manager, error) {
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if numLocks == 0 {
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return nil, errors.Errorf("must provide a non-zero number of locks!")
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}
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manager := new(InMemoryManager)
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manager.numLocks = numLocks
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manager.locks = make([]*Mutex, numLocks)
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var i uint32
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for i = 0; i < numLocks; i++ {
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lock := new(Mutex)
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lock.id = i
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manager.locks[i] = lock
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}
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return manager, nil
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}
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// AllocateLock allocates a lock from the manager.
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func (m *InMemoryManager) AllocateLock() (Locker, error) {
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m.localLock.Lock()
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defer m.localLock.Unlock()
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for _, lock := range m.locks {
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if !lock.allocated {
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lock.allocated = true
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return lock, nil
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}
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}
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return nil, errors.Errorf("all locks have been allocated")
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}
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// RetrieveLock retrieves a lock from the manager.
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func (m *InMemoryManager) RetrieveLock(id uint32) (Locker, error) {
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if id >= m.numLocks {
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return nil, errors.Errorf("given lock ID %d is too large - this manager only supports lock indexes up to %d", id, m.numLocks-1)
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}
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return m.locks[id], nil
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}
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// FreeAllLocks frees all locks.
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// This function is DANGEROUS. Please read the full comment in locks.go before
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// trying to use it.
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func (m *InMemoryManager) FreeAllLocks() error {
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for _, lock := range m.locks {
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lock.allocated = false
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}
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return nil
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}
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