/
semaphored_mutex.go
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/
semaphored_mutex.go
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// Copyright 2019 Authors of Cilium
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package lock
import (
"context"
"golang.org/x/sync/semaphore"
)
// SemaphoredMutex is a semaphored mutex that provides a RWLocker interface.
type SemaphoredMutex struct {
semaphore *semaphore.Weighted
}
// using the same value set in `go/src/rwmutex.go#rwmutexMaxReaders
const maxReaders = 1 << 30
// NewSemaphoredMutex returns a new SemaphoredMutex.
func NewSemaphoredMutex() SemaphoredMutex {
return SemaphoredMutex{
semaphore: semaphore.NewWeighted(maxReaders),
}
}
func (i *SemaphoredMutex) Lock() {
// It's fine ignoring error since the error is only caused by passing a
// context with a deadline.
i.semaphore.Acquire(context.Background(), maxReaders)
}
// UnlockToRLock releases the current lock for writing but it still keeps it
// for reading purposes.
func (i *SemaphoredMutex) UnlockToRLock() {
i.semaphore.Release(maxReaders - 1)
}
func (i *SemaphoredMutex) Unlock() {
i.semaphore.Release(maxReaders)
}
func (i *SemaphoredMutex) RLock() {
// It's fine ignoring error since the error is only caused by passing a
// context with a deadline.
i.semaphore.Acquire(context.Background(), 1)
}
func (i *SemaphoredMutex) RUnlock() {
i.semaphore.Release(1)
}