Add lock manager to libpod runtime

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

libpod/lock/lock.go

@@ -41,11 +41,14 @@ type Locker interface {
 	// Lock locks the lock.
 	// This call MUST block until it successfully acquires the lock or
 	// encounters a fatal error.
-	Lock() error
+	// All errors must be handled internally, as they are not returned. For
+	// the most part, panicking should be appropriate.
+	Lock()
 	// Unlock unlocks the lock.
-	// A call to Unlock() on a lock that is already unlocked lock MUST
-	// error.
-	Unlock() error
+	// All errors must be handled internally, as they are not returned. For
+	// the most part, panicking should be appropriate.
+	// This includes unlocking locks which are already unlocked.
+	Unlock()
 	// Free deallocates the underlying lock, allowing its reuse by other
 	// pods and containers.
 	// The lock MUST still be usable after a Free() - some libpod instances

libpod/lock/shm/shm_lock.go

@@ -12,9 +12,13 @@ import (
 	"unsafe"
 
 	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
 )
 
-const (
+var (
+	// BitmapSize is the size of the bitmap used when managing SHM locks.
+	// an SHM lock manager's max locks will be rounded up to a multiple of
+	// this number.
 	BitmapSize uint32 = uint32(C.bitmap_size_c)
 )
 
@@ -51,6 +55,8 @@ func CreateSHMLock(path string, numLocks uint32) (*SHMLocks, error) {
 	locks.maxLocks = uint32(lockStruct.num_locks)
 	locks.valid = true
 
+	logrus.Debugf("Initialized SHM lock manager at path %s", path)
+
 	return locks, nil
 }
 

libpod/lock/shm_lock_manager_linux.go

@@ -73,13 +73,17 @@ func (l *SHMLock) ID() uint32 {
 }
 
 // Lock acquires the lock.
-func (l *SHMLock) Lock() error {
-	return l.manager.locks.LockSemaphore(l.lockID)
+func (l *SHMLock) Lock() {
+	if err := l.manager.locks.LockSemaphore(l.lockID); err != nil {
+		panic(err.Error())
+	}
 }
 
 // Unlock releases the lock.
-func (l *SHMLock) Unlock() error {
-	return l.manager.locks.UnlockSemaphore(l.lockID)
+func (l *SHMLock) Unlock() {
+	if err := l.manager.locks.UnlockSemaphore(l.lockID); err != nil {
+		panic(err.Error())
+	}
 }
 
 // Free releases the lock, allowing it to be reused.