mirror of
https://github.com/go-gitea/gitea
synced 2024-11-24 20:02:48 +01:00
70 lines
2 KiB
Go
70 lines
2 KiB
Go
// Copyright 2016 The Gogs Authors. All rights reserved.
|
|
// Use of this source code is governed by a MIT-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package sync
|
|
|
|
import (
|
|
"sync"
|
|
)
|
|
|
|
// ExclusivePool is a pool of non-identical instances
|
|
// that only one instance with same identity is in the pool at a time.
|
|
// In other words, only instances with different identities can be in
|
|
// the pool the same time. If another instance with same identity tries
|
|
// to get into the pool, it hangs until previous instance left the pool.
|
|
//
|
|
// This pool is particularly useful for performing tasks on same resource
|
|
// on the file system in different goroutines.
|
|
type ExclusivePool struct {
|
|
lock sync.Mutex
|
|
|
|
// pool maintains locks for each instance in the pool.
|
|
pool map[string]*sync.Mutex
|
|
|
|
// count maintains the number of times an instance with same identity checks in
|
|
// to the pool, and should be reduced to 0 (removed from map) by checking out
|
|
// with same number of times.
|
|
// The purpose of count is to delete lock when count down to 0 and recycle memory
|
|
// from map object.
|
|
count map[string]int
|
|
}
|
|
|
|
// NewExclusivePool initializes and returns a new ExclusivePool object.
|
|
func NewExclusivePool() *ExclusivePool {
|
|
return &ExclusivePool{
|
|
pool: make(map[string]*sync.Mutex),
|
|
count: make(map[string]int),
|
|
}
|
|
}
|
|
|
|
// CheckIn checks in an instance to the pool and hangs while instance
|
|
// with same identity is using the lock.
|
|
func (p *ExclusivePool) CheckIn(identity string) {
|
|
p.lock.Lock()
|
|
|
|
lock, has := p.pool[identity]
|
|
if !has {
|
|
lock = &sync.Mutex{}
|
|
p.pool[identity] = lock
|
|
}
|
|
p.count[identity]++
|
|
|
|
p.lock.Unlock()
|
|
lock.Lock()
|
|
}
|
|
|
|
// CheckOut checks out an instance from the pool and releases the lock
|
|
// to let other instances with same identity to grab the lock.
|
|
func (p *ExclusivePool) CheckOut(identity string) {
|
|
p.lock.Lock()
|
|
defer p.lock.Unlock()
|
|
|
|
p.pool[identity].Unlock()
|
|
if p.count[identity] == 1 {
|
|
delete(p.pool, identity)
|
|
delete(p.count, identity)
|
|
} else {
|
|
p.count[identity]--
|
|
}
|
|
}
|