Fix memory-leak in CList; Patched with DetachPrev/DetachHead
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parent
76189fde0d
commit
80c7e26bee
53
clist.go
53
clist.go
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@ -5,6 +5,8 @@ The purpose of CList is to provide a goroutine-safe linked-list.
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This list can be traversed concurrently by any number of goroutines.
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However, removed CElements cannot be added back.
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NOTE: Not all methods of container/list are (yet) implemented.
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NOTE: Removed elements need to NukePrev or NukeNext consistently
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to ensure garbage collection of removed elements.
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*/
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import (
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@ -74,25 +76,45 @@ func (e *CElement) Removed() bool {
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return atomic.LoadUint32(&(e.removed)) > 0
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}
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func (e *CElement) DetachNext() {
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e.setNextAtomic(nil)
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e.nextWg.Done()
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}
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func (e *CElement) DetachPrev() {
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e.setPrevAtomic(nil)
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e.prevWg.Done()
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}
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func (e *CElement) setNextAtomic(next *CElement) {
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oldNext := (*CElement)(atomic.LoadPointer(&e.next))
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if next == nil && oldNext != nil {
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e.nextWg.Add(1) // NOTE: There is still a race condition for waiters, so we for-loop.
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}
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atomic.StorePointer(&(e.next), unsafe.Pointer(next))
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if next != nil && oldNext == nil {
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e.nextWg.Done()
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for {
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oldNext := atomic.LoadPointer(&e.next)
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if !atomic.CompareAndSwapPointer(&(e.next), oldNext, unsafe.Pointer(next)) {
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continue
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}
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if next == nil && oldNext != nil { // We for-loop in NextWait() so race is ok
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e.nextWg.Add(1)
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}
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if next != nil && oldNext == nil {
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e.nextWg.Done()
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}
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return
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}
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}
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func (e *CElement) setPrevAtomic(prev *CElement) {
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oldPrev := (*CElement)(atomic.LoadPointer(&e.prev))
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if prev == nil && oldPrev != nil {
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e.prevWg.Add(1) // NOTE: There is still a race condition for waiters, so we for-loop.
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}
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atomic.StorePointer(&(e.prev), unsafe.Pointer(prev))
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if prev != nil && oldPrev == nil {
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e.prevWg.Done()
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for {
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oldPrev := atomic.LoadPointer(&e.prev)
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if !atomic.CompareAndSwapPointer(&(e.prev), oldPrev, unsafe.Pointer(prev)) {
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continue
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}
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if prev == nil && oldPrev != nil { // We for-loop in PrevWait() so race is ok
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e.prevWg.Add(1)
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}
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if prev != nil && oldPrev == nil {
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e.prevWg.Done()
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}
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return
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}
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}
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@ -100,6 +122,8 @@ func (e *CElement) setRemovedAtomic() {
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atomic.StoreUint32(&(e.removed), 1)
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}
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//--------------------------------------------------------------------------------
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// CList represents a linked list.
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// The zero value for CList is an empty list ready to use.
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// Operations are goroutine-safe.
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@ -201,6 +225,7 @@ func (l *CList) PushBack(v interface{}) *CElement {
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return e
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}
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// CONTRACT: Caller must call e.DetachPrev() and/or e.DetachNext() to avoid memory leaks.
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// NOTE: As per the contract of CList, removed elements cannot be added back.
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func (l *CList) Remove(e *CElement) interface{} {
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l.mtx.Lock()
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