mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-23 10:42:12 +00:00
106 lines
2.2 KiB
Go
106 lines
2.2 KiB
Go
package mutexes
|
|
|
|
import (
|
|
"sync"
|
|
)
|
|
|
|
// MutexMap is a structure that allows having a map of self-evicting mutexes
|
|
// by key. You do not need to worry about managing the contents of the map,
|
|
// only requesting RLock/Lock for keys, and ensuring to call the returned
|
|
// unlock functions.
|
|
type MutexMap struct {
|
|
// NOTE:
|
|
// Individual keyed mutexes should ONLY ever
|
|
// be locked within the protection of the outer
|
|
// mapMu lock. If you lock these outside the
|
|
// protection of this, there is a chance for
|
|
// deadlocks
|
|
|
|
mus map[string]RWMutex
|
|
mapMu sync.Mutex
|
|
pool sync.Pool
|
|
}
|
|
|
|
// NewMap returns a new MutexMap instance based on supplied
|
|
// RWMutex allocator function, nil implies use default
|
|
func NewMap(newFn func() RWMutex) MutexMap {
|
|
if newFn == nil {
|
|
newFn = NewRW
|
|
}
|
|
return MutexMap{
|
|
mus: make(map[string]RWMutex),
|
|
mapMu: sync.Mutex{},
|
|
pool: sync.Pool{
|
|
New: func() interface{} {
|
|
return newFn()
|
|
},
|
|
},
|
|
}
|
|
}
|
|
|
|
func (mm *MutexMap) evict(key string, mu RWMutex) {
|
|
// Acquire map lock
|
|
mm.mapMu.Lock()
|
|
|
|
// Toggle mutex lock to
|
|
// ensure it is unused
|
|
unlock := mu.Lock()
|
|
unlock()
|
|
|
|
// Delete mutex key
|
|
delete(mm.mus, key)
|
|
mm.mapMu.Unlock()
|
|
|
|
// Release to pool
|
|
mm.pool.Put(mu)
|
|
}
|
|
|
|
// RLock acquires a mutex read lock for supplied key, returning an RUnlock function
|
|
func (mm *MutexMap) RLock(key string) func() {
|
|
return mm.getLock(key, func(mu RWMutex) func() {
|
|
return mu.RLock()
|
|
})
|
|
}
|
|
|
|
// Lock acquires a mutex lock for supplied key, returning an Unlock function
|
|
func (mm *MutexMap) Lock(key string) func() {
|
|
return mm.getLock(key, func(mu RWMutex) func() {
|
|
return mu.Lock()
|
|
})
|
|
}
|
|
|
|
func (mm *MutexMap) getLock(key string, doLock func(RWMutex) func()) func() {
|
|
// Get map lock
|
|
mm.mapMu.Lock()
|
|
|
|
// Look for mutex
|
|
mu, ok := mm.mus[key]
|
|
if ok {
|
|
// Lock and return
|
|
// its unlocker func
|
|
unlock := doLock(mu)
|
|
mm.mapMu.Unlock()
|
|
return unlock
|
|
}
|
|
|
|
// Note: even though the mutex data structure is
|
|
// small, benchmarking does actually show that pooled
|
|
// alloc of mutexes here is faster
|
|
|
|
// Acquire mu + add
|
|
mu = mm.pool.Get().(RWMutex)
|
|
mm.mus[key] = mu
|
|
|
|
// Lock mutex + unlock map
|
|
unlockFn := doLock(mu)
|
|
mm.mapMu.Unlock()
|
|
|
|
return func() {
|
|
// Unlock mutex
|
|
unlockFn()
|
|
|
|
// Release function
|
|
go mm.evict(key, mu)
|
|
}
|
|
}
|