fix LibVirtPoolSync

Declare methods of LibVirtPoolSync as pointers since otherwise the
entire construct is ineffective. Callers of `AcquireLock` are now
responsible for making sure that the mutex is locked.

This will prevent the following errors:
	* fatal error: concurrent map writes
	* panic: sync: unlock of unlocked mutex

This fixes #121.

Signed-off-by: Thomas Hipp <[email protected]>

Author: Thomas Hipp

libvirt/cloudinit_def.go

@@ -62,7 +62,11 @@ func (ci *defCloudInit) CreateAndUpload(virConn *libvirt.Connect) (string, error
 	}
 	defer pool.Free()
 
-	PoolSync.AcquireLock(ci.PoolName)
+	for {
+		if PoolSync.AcquireLock(ci.PoolName) {
+			break
+		}
+	}
 	defer PoolSync.ReleaseLock(ci.PoolName)
 
 	// Refresh the pool of the volume so that libvirt knows it is

libvirt/coreos_ignition_def.go

@@ -38,7 +38,11 @@ func (ign *defIgnition) CreateAndUpload(virConn *libvirt.Connect) (string, error
 	}
 	defer pool.Free()
 
-	PoolSync.AcquireLock(ign.PoolName)
+	for {
+		if PoolSync.AcquireLock(ign.PoolName) {
+			break
+		}
+	}
 	defer PoolSync.ReleaseLock(ign.PoolName)
 
 	// Refresh the pool of the volume so that libvirt knows it is

libvirt/pool_sync.go

@@ -1,49 +1,56 @@
 package libvirt
 
-import (
-	"sync"
-)
+import "sync"
 
 // LibVirtPoolSync makes possible to synchronize operations
 // against libvirt pools.
 // Doing pool.Refresh() operations while uploading or removing
 // a volume into the pool causes errors inside of libvirtd
 type LibVirtPoolSync struct {
 	PoolLocks     map[string]*sync.Mutex
+	PoolLocked    map[string]bool
 	internalMutex sync.Mutex
 }
 
 // Allocate a new instance of LibVirtPoolSync
-func NewLibVirtPoolSync() LibVirtPoolSync {
+func NewLibVirtPoolSync() *LibVirtPoolSync {
 	pool := LibVirtPoolSync{}
 	pool.PoolLocks = make(map[string]*sync.Mutex)
+	pool.PoolLocked = make(map[string]bool)
 
-	return pool
+	return &pool
 }
 
-// Acquire a lock for the specified pool
-func (ps LibVirtPoolSync) AcquireLock(pool string) {
+// Acquire a lock for the specified pool. If the mutex is already locked, the
+// method returns false, and does not block. It returns true, if the lock
+// could be acquired.
+func (ps *LibVirtPoolSync) AcquireLock(pool string) bool {
 	ps.internalMutex.Lock()
 	defer ps.internalMutex.Unlock()
 
-	lock, exists := ps.PoolLocks[pool]
-	if !exists {
-		lock = new(sync.Mutex)
-		ps.PoolLocks[pool] = lock
+	if ps.PoolLocks[pool] == nil {
+		ps.PoolLocks[pool] = new(sync.Mutex)
+	} else {
+		if ps.PoolLocked[pool] {
+			return false
+		}
 	}
 
-	lock.Lock()
+	ps.PoolLocks[pool].Lock()
+	ps.PoolLocked[pool] = true
+
+	return true
 }
 
 // Release the look for the specified pool
-func (ps LibVirtPoolSync) ReleaseLock(pool string) {
+func (ps *LibVirtPoolSync) ReleaseLock(pool string) {
 	ps.internalMutex.Lock()
 	defer ps.internalMutex.Unlock()
 
-	lock, exists := ps.PoolLocks[pool]
-	if !exists {
+	if ps.PoolLocks[pool] == nil {
 		return
 	}
 
-	lock.Unlock()
+	ps.PoolLocks[pool].Unlock()
+	ps.PoolLocked[pool] = false
 }

libvirt/resource_libvirt_volume.go

@@ -90,7 +90,11 @@ func resourceLibvirtVolumeCreate(d *schema.ResourceData, meta interface{}) error
 		poolName = d.Get("pool").(string)
 	}
 
-	PoolSync.AcquireLock(poolName)
+	for {
+		if PoolSync.AcquireLock(poolName) {
+			break
+		}
+	}
 	defer PoolSync.ReleaseLock(poolName)
 
 	pool, err := virConn.LookupStoragePoolByName(poolName)

libvirt/utils.go

@@ -78,7 +78,11 @@ func RemoveVolume(virConn *libvirt.Connect, key string) error {
 		return fmt.Errorf("Error retrieving name of volume: %s", err)
 	}
 
-	PoolSync.AcquireLock(poolName)
+	for {
+		if PoolSync.AcquireLock(poolName) {
+			break
+		}
+	}
 	defer PoolSync.ReleaseLock(poolName)
 
 	WaitForSuccess("Error refreshing pool for volume", func() error {