@@ -0,0 +1,51 @@
+package mutexkv
+
+import (
+	"log"
+	"sync"
+)
+
+// MutexKV is a simple key/value store for arbitrary mutexes. It can be used to
+// serialize changes across arbitrary collaborators that share knowledge of the
+// keys they must serialize on.
+//
+// The initial use case is to let aws_security_group_rule resources serialize
+// their access to individual security groups based on SG ID.
+type MutexKV struct {
+	lock  sync.Mutex
+	store map[string]*sync.Mutex
+}
+
+// Locks the mutex for the given key. Caller is responsible for calling Unlock
+// for the same key.
+func (m *MutexKV) Lock(key string) {
+	log.Printf("[DEBUG] Locking %q", key)
+	m.get(key).Lock()
+	log.Printf("[DEBUG] Locked %q", key)
+}
+
+// Unlock the mutex for the given key. Caller must have called Lock for the same key first.
+func (m *MutexKV) Unlock(key string) {
+	log.Printf("[DEBUG] Unlocking %q", key)
+	m.get(key).Unlock()
+	log.Printf("[DEBUG] Unlocked %q", key)
+}
+
+// Returns a mutex for the given key, no guarantee of its lock status.
+func (m *MutexKV) get(key string) *sync.Mutex {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+	mutex, ok := m.store[key]
+	if !ok {
+		mutex = &sync.Mutex{}
+		m.store[key] = mutex
+	}
+	return mutex
+}
+
+// Returns a properly initialized MutexKV.
+func NewMutexKV() *MutexKV {
+	return &MutexKV{
+		store: make(map[string]*sync.Mutex),
+	}
+}
@@ -0,0 +1,67 @@
+package mutexkv
+
+import (
+	"testing"
+	"time"
+)
+
+func TestMutexKVLock(t *testing.T) {
+	mkv := NewMutexKV()
+
+	mkv.Lock("foo")
+
+	doneCh := make(chan struct{})
+
+	go func() {
+		mkv.Lock("foo")
+		close(doneCh)
+	}()
+
+	select {
+	case <-doneCh:
+		t.Fatal("Second lock was able to be taken. This shouldn't happen.")
+	case <-time.After(50 * time.Millisecond):
+		// pass
+	}
+}
+
+func TestMutexKVUnlock(t *testing.T) {
+	mkv := NewMutexKV()
+
+	mkv.Lock("foo")
+	mkv.Unlock("foo")
+
+	doneCh := make(chan struct{})
+
+	go func() {
+		mkv.Lock("foo")
+		close(doneCh)
+	}()
+
+	select {
+	case <-doneCh:
+		// pass
+	case <-time.After(50 * time.Millisecond):
+		t.Fatal("Second lock blocked after unlock. This shouldn't happen.")
+	}
+}
+
+func TestMutexKVDifferentKeys(t *testing.T) {
+	mkv := NewMutexKV()
+
+	mkv.Lock("foo")
+
+	doneCh := make(chan struct{})
+
+	go func() {
+		mkv.Lock("bar")
+		close(doneCh)
+	}()
+
+	select {
+	case <-doneCh:
+		// pass
+	case <-time.After(50 * time.Millisecond):
+		t.Fatal("Second lock on a different key blocked. This shouldn't happen.")
+	}
+}
@@ -1,10 +1,10 @@
 package openstack
 
 import (
-	"github.com/hashicorp/terraform-plugin-sdk/helper/mutexkv"
 	"github.com/hashicorp/terraform-plugin-sdk/helper/schema"
 	"github.com/hashicorp/terraform-plugin-sdk/meta"
 	"github.com/hashicorp/terraform-plugin-sdk/terraform"
+	"github.com/terraform-provider-openstack/terraform-provider-openstack/openstack/internal/mutexkv"
 
 	"github.com/gophercloud/utils/terraform/auth"
 )
 
@@ -6,10 +6,10 @@ import (
 	"os"
 	"testing"
 
-	"github.com/hashicorp/terraform-plugin-sdk/helper/mutexkv"
 	"github.com/hashicorp/terraform-plugin-sdk/helper/pathorcontents"
 	"github.com/hashicorp/terraform-plugin-sdk/helper/schema"
 	"github.com/hashicorp/terraform-plugin-sdk/terraform"
+	"github.com/terraform-provider-openstack/terraform-provider-openstack/openstack/internal/mutexkv"
 
 	"github.com/gophercloud/utils/terraform/auth"
 )