frostfs-node/pkg/util/sync/key_locker.go

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package sync
import "sync"
type locker struct {
mtx sync.Mutex
waiters int // not protected by mtx, must used outer mutex to update concurrently
}
type KeyLocker[K comparable] struct {
lockers map[K]*locker
lockersMtx sync.Mutex
}
func NewKeyLocker[K comparable]() *KeyLocker[K] {
return &KeyLocker[K]{
lockers: make(map[K]*locker),
}
}
func (l *KeyLocker[K]) Lock(key K) {
l.lockersMtx.Lock()
if locker, found := l.lockers[key]; found {
locker.waiters++
l.lockersMtx.Unlock()
locker.mtx.Lock()
return
}
locker := &locker{
waiters: 1,
}
locker.mtx.Lock()
l.lockers[key] = locker
l.lockersMtx.Unlock()
}
func (l *KeyLocker[K]) Unlock(key K) {
l.lockersMtx.Lock()
defer l.lockersMtx.Unlock()
locker, found := l.lockers[key]
if !found {
return
}
if locker.waiters == 1 {
delete(l.lockers, key)
}
locker.waiters--
locker.mtx.Unlock()
}