diff --git a/namespace-lock.go b/namespace-lock.go index 018747a6e..9ba1af488 100644 --- a/namespace-lock.go +++ b/namespace-lock.go @@ -16,7 +16,11 @@ package main -import "sync" +import ( + "sync" + + "github.com/Sirupsen/logrus" +) // nsParam - carries name space resource. type nsParam struct { @@ -48,11 +52,9 @@ func initNSLock() { } } -// Lock - locks the given resource for writes, using a previously -// allocated name space lock or initializing a new one. -func (n *nsLockMap) Lock(volume, path string) { +// Lock the namespace resource. +func (n *nsLockMap) lock(volume, path string, readLock bool) { n.mutex.Lock() - defer n.mutex.Unlock() param := nsParam{volume, path} nsLk, found := n.lockMap[param] @@ -61,68 +63,70 @@ func (n *nsLockMap) Lock(volume, path string) { RWMutex: &sync.RWMutex{}, ref: 0, } + n.lockMap[param] = nsLk } - - // Acquire a write lock and update reference counter. - nsLk.Lock() nsLk.ref++ + // Unlock map before Locking NS which might block. + n.mutex.Unlock() - n.lockMap[param] = nsLk + // Locking here can block. + if readLock { + nsLk.RLock() + } else { + nsLk.Lock() + } +} + +// Unlock the namespace resource. +func (n *nsLockMap) unlock(volume, path string, readLock bool) { + // nsLk.Unlock() will not block, hence locking the map for the entire function is fine. + n.mutex.Lock() + defer n.mutex.Unlock() + + param := nsParam{volume, path} + if nsLk, found := n.lockMap[param]; found { + if readLock { + nsLk.RUnlock() + } else { + nsLk.Unlock() + } + if nsLk.ref == 0 { + log.WithFields(logrus.Fields{ + "volume": volume, + "path": path, + }).Error("ref count in NS lock can not be 0.") + } + if nsLk.ref != 0 { + nsLk.ref-- + } + if nsLk.ref == 0 { + // Remove from the map if there are no more references. + delete(n.lockMap, param) + } + } +} + +// Lock - locks the given resource for writes, using a previously +// allocated name space lock or initializing a new one. +func (n *nsLockMap) Lock(volume, path string) { + readLock := false + n.lock(volume, path, readLock) } // Unlock - unlocks any previously acquired write locks. func (n *nsLockMap) Unlock(volume, path string) { - n.mutex.Lock() - defer n.mutex.Unlock() - - param := nsParam{volume, path} - if nsLk, found := n.lockMap[param]; found { - // Unlock a write lock and update reference counter. - nsLk.Unlock() - if nsLk.ref != 0 { - nsLk.ref-- - } - if nsLk.ref != 0 { - n.lockMap[param] = nsLk - } - } + readLock := false + n.unlock(volume, path, readLock) } // RLock - locks any previously acquired read locks. func (n *nsLockMap) RLock(volume, path string) { - n.mutex.Lock() - defer n.mutex.Unlock() - - param := nsParam{volume, path} - nsLk, found := n.lockMap[param] - if !found { - nsLk = &nsLock{ - RWMutex: &sync.RWMutex{}, - ref: 0, - } - } - - // Acquire a read lock and update reference counter. - nsLk.RLock() - nsLk.ref++ - - n.lockMap[param] = nsLk + readLock := true + n.lock(volume, path, readLock) } // RUnlock - unlocks any previously acquired read locks. func (n *nsLockMap) RUnlock(volume, path string) { - n.mutex.Lock() - defer n.mutex.Unlock() - - param := nsParam{volume, path} - if nsLk, found := n.lockMap[param]; found { - // Unlock a read lock and update reference counter. - nsLk.RUnlock() - if nsLk.ref != 0 { - nsLk.ref-- - } - if nsLk.ref != 0 { - n.lockMap[param] = nsLk - } - } + readLock := true + n.unlock(volume, path, readLock) }