53 lines
931 B
Go
53 lines
931 B
Go
package rlock
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import (
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"sync"
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"time"
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)
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// RLock is like [sync.Mutex], but permits recursive locking.
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type RLock struct {
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m sync.Mutex // m is held internally
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held bool
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holder int
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counter uint64
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}
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// Lock acquires this lock with the given id, and blocks until it can be aquired.
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// Concurrent locks with the same ids do not block; however each should be unlocked with a call to unlock.
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func (rm *RLock) Lock(id int) {
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loop:
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for {
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rm.m.Lock()
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switch {
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case !rm.held:
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rm.held = true
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rm.holder = id
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break loop
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case rm.held && rm.holder == id:
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break loop
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}
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rm.m.Unlock()
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time.Sleep(time.Millisecond) // spinning!
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}
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rm.counter++
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rm.m.Unlock()
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}
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// Unlock releases the lock
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func (rm *RLock) Unlock() {
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rm.m.Lock()
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defer rm.m.Unlock()
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if !rm.held || rm.counter <= 0 {
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panic("RLock: Unlock() without Lock()")
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}
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rm.counter--
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if rm.counter == 0 {
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rm.held = false
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rm.holder = 0
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}
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}
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