diff -u b/core/includes/common.inc b/core/includes/common.inc
--- b/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -3200,7 +3200,7 @@
   drupal_alter('queue_info', $queues);
 
   // Try to acquire cron lock.
-  if (!lock()->acquire('cron', 240.0)) {
+  if (!\Drupal::lock()->acquire('cron', 240.0)) {
     // Cron is still running normally.
     watchdog('cron', 'Attempting to re-run cron while it is already running.', array(), WATCHDOG_WARNING);
   }
@@ -3229,7 +3229,7 @@
     watchdog('cron', 'Cron run completed.', array(), WATCHDOG_NOTICE);
 
     // Release cron lock.
-    lock()->release('cron');
+    \Drupal::lock()->release('cron');
 
     // Return TRUE so other functions can check if it did run successfully
     $return = TRUE;
@@ -3262,7 +3262,7 @@
     watchdog('cron', 'Cron run completed.', array(), WATCHDOG_NOTICE);
 
     // Release cron lock.
-    Drupal::lock()->release('cron');
+    lock()->release('cron');
 
     // Return TRUE so other functions can check if it did run successfully
     $return = TRUE;
diff -u b/core/includes/menu.inc b/core/includes/menu.inc
--- b/core/includes/menu.inc
+++ b/core/includes/menu.inc
@@ -2521,11 +2521,11 @@
  *   in parallel and the current thread just waited for completion.
  */
 function menu_router_rebuild() {
-  if (!lock()->acquire(__FUNCTION__)) {
+  if (!\Drupal::lock()->acquire(__FUNCTION__)) {
     // Wait for another request that is already doing this work.
     // We choose to block here since otherwise the router item may not
     // be available during routing resulting in a 404.
-    lock()->wait(__FUNCTION__);
+    \Drupal::lock()->wait(__FUNCTION__);
     return FALSE;
   }
 
@@ -2545,7 +2545,7 @@
     watchdog_exception('menu', $e);
   }
 
-  lock()->release(__FUNCTION__);
+  \Drupal::lock()->release(__FUNCTION__);
   return TRUE;
 }
 
@@ -2715,11 +2715,11 @@
  *   in parallel and the current thread just waited for completion.
  */
 function menu_router_rebuild() {
-  if (!Drupal::lock()->acquire(__FUNCTION__)) {
+  if (!lock()->acquire(__FUNCTION__)) {
     // Wait for another request that is already doing this work.
     // We choose to block here since otherwise the router item may not
     // be available during routing resulting in a 404.
-    Drupal::lock()->wait(__FUNCTION__);
+    lock()->wait(__FUNCTION__);
     return FALSE;
   }
 
@@ -2739,7 +2739,7 @@
     watchdog_exception('menu', $e);
   }
 
-  Drupal::lock()->release(__FUNCTION__);
+  lock()->release(__FUNCTION__);
   return TRUE;
 }
 
diff -u b/core/lib/Drupal/Core/Utility/CacheArray.php b/core/lib/Drupal/Core/Utility/CacheArray.php
--- b/core/lib/Drupal/Core/Utility/CacheArray.php
+++ b/core/lib/Drupal/Core/Utility/CacheArray.php
@@ -201,13 +201,13 @@
     // Lock cache writes to help avoid stampedes.
     // To implement locking for cache misses, override __construct().
     $lock_name = $this->cid . ':' . $this->bin;
-    if (!$lock || Drupal::lock()->acquire($lock_name)) {
+    if (!$lock || \Drupal::lock()->acquire($lock_name)) {
       if ($cached = cache($this->bin)->get($this->cid)) {
         $data = $cached->data + $data;
       }
       cache($this->bin)->set($this->cid, $data, CacheBackendInterface::CACHE_PERMANENT, $this->tags);
       if ($lock) {
-          Drupal::lock()->release($lock_name);
+        \Drupal::lock()->release($lock_name);
       }
     }
   }
reverted:
--- b/core/lib/Drupal/Core/Utility/ThemeRegistry.php
+++ a/core/lib/Drupal/Core/Utility/ThemeRegistry.php
@@ -126,7 +126,7 @@
    */
   public function set($data, $lock = TRUE) {
     $lock_name = $this->cid . ':' . $this->bin;
+    if (!$lock || lock()->acquire($lock_name)) {
-    if (!$lock || Drupal::lock()->acquire($lock_name)) {
       if ($cached = cache($this->bin)->get($this->cid)) {
         // Use array merge instead of union so that filled in values in $data
         // overwrite empty values in the current cache.
@@ -138,7 +138,7 @@
       }
       cache($this->bin)->set($this->cid, $data, CacheBackendInterface::CACHE_PERMANENT, $this->tags);
       if ($lock) {
+        lock()->release($lock_name);
-        Drupal::lock()->release($lock_name);
       }
     }
   }
reverted:
--- b/core/modules/comment/lib/Drupal/comment/Plugin/Core/Entity/Comment.php
+++ a/core/modules/comment/lib/Drupal/comment/Plugin/Core/Entity/Comment.php
@@ -327,7 +327,7 @@
    */
   protected function releaseThreadLock() {
     if ($this->threadLock) {
+      lock()->release($this->threadLock);
-      Drupal::lock()->release($this->threadLock);
       $this->threadLock = '';
     }
   }
diff -u b/core/modules/system/lib/Drupal/system/Tests/Lock/LockFunctionalTest.php b/core/modules/system/lib/Drupal/system/Tests/Lock/LockFunctionalTest.php
--- b/core/modules/system/lib/Drupal/system/Tests/Lock/LockFunctionalTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Lock/LockFunctionalTest.php
@@ -36,33 +36,33 @@
     $lock_acquired = 'TRUE: Lock successfully acquired in system_test_lock_acquire()';
     $lock_not_acquired = 'FALSE: Lock not acquired in system_test_lock_acquire()';
-    $this->assertTrue(lock()->acquire('system_test_lock_acquire'), 'Lock acquired by this request.', 'Lock');
-    $this->assertTrue(lock()->acquire('system_test_lock_acquire'), 'Lock extended by this request.', 'Lock');
-    Drupal::lock()->release('system_test_lock_acquire');
+    $this->assertTrue(\Drupal::lock()->acquire('system_test_lock_acquire'), 'Lock acquired by this request.', 'Lock');
+    $this->assertTrue(\Drupal::lock()->acquire('system_test_lock_acquire'), 'Lock extended by this request.', 'Lock');
+    \Drupal::lock()->release('system_test_lock_acquire');
 
     // Cause another request to acquire the lock.
     $this->drupalGet('system-test/lock-acquire');
     $this->assertText($lock_acquired, 'Lock acquired by the other request.', 'Lock');
     // The other request has finished, thus it should have released its lock.
-    $this->assertTrue(Drupal::lock()->acquire('system_test_lock_acquire'), 'Lock acquired by this request.', 'Lock');
+    $this->assertTrue(\Drupal::lock()->acquire('system_test_lock_acquire'), 'Lock acquired by this request.', 'Lock');
     // This request holds the lock, so the other request cannot acquire it.
     $this->drupalGet('system-test/lock-acquire');
     $this->assertText($lock_not_acquired, 'Lock not acquired by the other request.', 'Lock');
-    Drupal::lock()->release('system_test_lock_acquire');
+    \Drupal::lock()->release('system_test_lock_acquire');
 
     // Try a very short timeout and lock breaking.
-    $this->assertTrue(Drupal::lock()->acquire('system_test_lock_acquire', 0.5), 'Lock acquired by this request.', 'Lock');
+    $this->assertTrue(\Drupal::lock()->acquire('system_test_lock_acquire', 0.5), 'Lock acquired by this request.', 'Lock');
     sleep(1);
     // The other request should break our lock.
     $this->drupalGet('system-test/lock-acquire');
     $this->assertText($lock_acquired, 'Lock acquired by the other request, breaking our lock.', 'Lock');
     // We cannot renew it, since the other thread took it.
-    $this->assertFalse(Drupal::lock()->acquire('system_test_lock_acquire'), 'Lock cannot be extended by this request.', 'Lock');
+    $this->assertFalse(\Drupal::lock()->acquire('system_test_lock_acquire'), 'Lock cannot be extended by this request.', 'Lock');
 
     // Check the shut-down function.
     $lock_acquired_exit = 'TRUE: Lock successfully acquired in system_test_lock_exit()';
     $lock_not_acquired_exit = 'FALSE: Lock not acquired in system_test_lock_exit()';
     $this->drupalGet('system-test/lock-exit');
     $this->assertText($lock_acquired_exit, 'Lock acquired by the other request before exit.', 'Lock');
-    $this->assertTrue(lock()->acquire('system_test_lock_exit'), 'Lock acquired by this request after the other request exits.', 'Lock');
+    $this->assertTrue(\Drupal::lock()->acquire('system_test_lock_exit'), 'Lock acquired by this request after the other request exits.', 'Lock');
   }
 }
diff -u b/core/modules/system/tests/modules/system_test/system_test.module b/core/modules/system/tests/modules/system_test/system_test.module
--- b/core/modules/system/tests/modules/system_test/system_test.module
+++ b/core/modules/system/tests/modules/system_test/system_test.module
@@ -77,8 +77,8 @@
  * @deprecated \Drupal\system_test\Controller\SystemTestController::lockAcquire()
  */
 function system_test_lock_acquire() {
-  if (lock()->acquire('system_test_lock_acquire')) {
-    lock()->release('system_test_lock_acquire');
+  if (\Drupal::lock()->acquire('system_test_lock_acquire')) {
+    \Drupal::lock()->release('system_test_lock_acquire');
     return 'TRUE: Lock successfully acquired in system_test_lock_acquire()';
   }
   else {
@@ -92,7 +92,7 @@
  * @deprecated \Drupal\system_test\Controller\SystemTestController::lockExit()
  */
 function system_test_lock_exit() {
-  if (lock()->acquire('system_test_lock_exit', 900)) {
+  if (\Drupal::lock()->acquire('system_test_lock_exit', 900)) {
     echo 'TRUE: Lock successfully acquired in system_test_lock_exit()';
     // The shut-down function should release the lock.
     exit();
@@ -170,8 +170,8 @@
  * Try to acquire a named lock and report the outcome.
  */
 function system_test_lock_acquire() {
-  if (Drupal::lock()->acquire('system_test_lock_acquire')) {
-    Drupal::lock()->release('system_test_lock_acquire');
+  if (lock()->acquire('system_test_lock_acquire')) {
+    lock()->release('system_test_lock_acquire');
     return 'TRUE: Lock successfully acquired in system_test_lock_acquire()';
   }
   else {
only in patch2:
unchanged:
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -3015,70 +3015,3 @@ function drupal_check_memory_limit($required, $memory_limit = NULL) {
   //   the operation.
   return ((!$memory_limit) || ($memory_limit == -1) || (parse_size($memory_limit) >= parse_size($required)));
 }
-
-/**
- * @defgroup lock Locking mechanisms
- * @{
- * Functions to coordinate long-running operations across requests.
- *
- * In most environments, multiple Drupal page requests (a.k.a. threads or
- * processes) will execute in parallel. This leads to potential conflicts or
- * race conditions when two requests execute the same code at the same time. A
- * common example of this is a rebuild like menu_router_rebuild() where we
- * invoke many hook implementations to get and process data from all active
- * modules, and then delete the current data in the database to insert the new
- * afterwards.
- *
- * This is a cooperative, advisory lock system. Any long-running operation
- * that could potentially be attempted in parallel by multiple requests should
- * try to acquire a lock before proceeding. By obtaining a lock, one request
- * notifies any other requests that a specific operation is in progress which
- * must not be executed in parallel.
- *
- * To use this API, pick a unique name for the lock. A sensible choice is the
- * name of the function performing the operation. A very simple example use of
- * this API:
- * @code
- * function mymodule_long_operation() {
- *   if (lock()->acquire('mymodule_long_operation')) {
- *     // Do the long operation here.
- *     // ...
- *     lock()->release('mymodule_long_operation');
- *   }
- * }
- * @endcode
- *
- * If a function acquires a lock it should always release it when the
- * operation is complete by calling lock()->release(), as in the example.
- *
- * A function that has acquired a lock may attempt to renew a lock (extend the
- * duration of the lock) by calling lock()->acquire() again during the operation.
- * Failure to renew a lock is indicative that another request has acquired
- * the lock, and that the current operation may need to be aborted.
- *
- * If a function fails to acquire a lock it may either immediately return, or
- * it may call lock()->wait() if the rest of the current page request requires
- * that the operation in question be complete. After lock()->wait() returns,
- * the function may again attempt to acquire the lock, or may simply allow the
- * page request to proceed on the assumption that a parallel request completed
- * the operation.
- *
- * lock()->acquire() and lock()->wait() will automatically break (delete) a lock
- * whose duration has exceeded the timeout specified when it was acquired.
- */
-
-/**
- * Get locking layer instance.
- *
- * @deprecated Use \Drupal::lock() instead, or even better have the lock service
- *   injected into your object.
- *
- * @return \Drupal\Core\Lock\LockBackendInterface
- */
-function lock() {
-  return \Drupal::lock();
-}
-
-/**
- * @} End of "defgroup lock".
- */