diff --git a/ext/opcache/ZendAccelerator.c b/ext/opcache/ZendAccelerator.c
index 48a07760d981..ec33c69eb2f0 100644
--- a/ext/opcache/ZendAccelerator.c
+++ b/ext/opcache/ZendAccelerator.c
@@ -135,11 +135,7 @@ static void preload_shutdown(void);
 static void preload_activate(void);
 static void preload_restart(void);
 
-#ifdef HAVE_STDATOMIC_H
-# define INCREMENT(v) (++ZCSG(v))
-# define DECREMENT(v) (--ZCSG(v))
-# define LOCKVAL(v)   atomic_load(&ZCSG(v))
-#elif defined(ZEND_WIN32)
+#ifdef ZEND_WIN32
 # define INCREMENT(v) InterlockedIncrement64(&ZCSG(v))
 # define DECREMENT(v) InterlockedDecrement64(&ZCSG(v))
 # define LOCKVAL(v)   (ZCSG(v))
@@ -277,7 +273,7 @@ static ZEND_INI_MH(accel_include_path_on_modify)
 
 static inline void accel_restart_enter(void)
 {
-#ifdef INCREMENT
+#ifdef ZEND_WIN32
 	INCREMENT(restart_in);
 #else
 	struct flock restart_in_progress;
@@ -296,7 +292,7 @@ static inline void accel_restart_enter(void)
 
 static inline void accel_restart_leave(void)
 {
-#ifdef DECREMENT
+#ifdef ZEND_WIN32
 	ZCSG(restart_in_progress) = false;
 	DECREMENT(restart_in);
 #else
@@ -317,9 +313,7 @@ static inline void accel_restart_leave(void)
 static inline int accel_restart_is_active(void)
 {
 	if (ZCSG(restart_in_progress)) {
-#ifdef LOCKVAL
-		return LOCKVAL(restart_in) != 0;
-#else
+#ifndef ZEND_WIN32
 		struct flock restart_check;
 
 		restart_check.l_type = F_WRLCK;
@@ -337,6 +331,8 @@ static inline int accel_restart_is_active(void)
 		} else {
 			return 1;
 		}
+#else
+		return LOCKVAL(restart_in) != 0;
 #endif
 	}
 	return 0;
@@ -345,7 +341,7 @@ static inline int accel_restart_is_active(void)
 /* Creates a read lock for SHM access */
 static inline zend_result accel_activate_add(void)
 {
-#ifdef INCREMENT
+#ifdef ZEND_WIN32
 	SHM_UNPROTECT();
 	INCREMENT(mem_usage);
 	SHM_PROTECT();
@@ -368,7 +364,7 @@ static inline zend_result accel_activate_add(void)
 /* Releases a lock for SHM access */
 static inline void accel_deactivate_sub(void)
 {
-#ifdef DECREMENT
+#ifdef ZEND_WIN32
 	if (ZCG(counted)) {
 		SHM_UNPROTECT();
 		DECREMENT(mem_usage);
@@ -391,7 +387,7 @@ static inline void accel_deactivate_sub(void)
 
 static inline void accel_unlock_all(void)
 {
-#ifdef DECREMENT
+#ifdef ZEND_WIN32
 	accel_deactivate_sub();
 #else
 	struct flock mem_usage_unlock_all;
@@ -832,7 +828,7 @@ static void accel_use_shm_interned_strings(void)
 	HANDLE_UNBLOCK_INTERRUPTIONS();
 }
 
-#ifndef LOCKVAL
+#ifndef ZEND_WIN32
 static inline void kill_all_lockers(struct flock *mem_usage_check)
 {
 	int tries;
@@ -899,7 +895,14 @@ static inline void kill_all_lockers(struct flock *mem_usage_check)
 
 static inline int accel_is_inactive(void)
 {
-#ifdef LOCKVAL
+#ifdef ZEND_WIN32
+	/* on Windows, we don't need kill_all_lockers() because SAPIs
+	   that work on Windows don't manage child processes (and we
+	   can't do anything about hanging threads anyway); therefore
+	   on Windows, we can simply manage this counter with atomics
+	   instead of flocks (atomics are much faster but they don't
+	   provide us with the PID of locker processes) */
+
 	if (LOCKVAL(mem_usage) == 0) {
 		return SUCCESS;
 	}
diff --git a/ext/opcache/ZendAccelerator.h b/ext/opcache/ZendAccelerator.h
index 6ecc2c2bc9df..bc92854c3557 100644
--- a/ext/opcache/ZendAccelerator.h
+++ b/ext/opcache/ZendAccelerator.h
@@ -55,14 +55,6 @@
 #include "zend_accelerator_hash.h"
 #include "zend_accelerator_debug.h"
 
-#ifdef HAVE_STDATOMIC_H
-# ifdef __cplusplus
-#  include <atomic>
-# else
-#  include <stdatomic.h>
-# endif
-#endif // HAVE_STDATOMIC_H
-
 #ifndef PHPAPI
 # ifdef ZEND_WIN32
 #  define PHPAPI __declspec(dllimport)
@@ -269,13 +261,7 @@ typedef struct _zend_accel_shared_globals {
 	bool       restart_pending;
 	zend_accel_restart_reason restart_reason;
 	bool       cache_status_before_restart;
-#ifdef HAVE_STDATOMIC_H
-# ifdef __cplusplus
-	std::atomic_llong mem_usage, restart_in;
-# else
-	atomic_llong mem_usage, restart_in;
-# endif
-#elif defined(ZEND_WIN32)
+#ifdef ZEND_WIN32
 	LONGLONG   mem_usage;
 	LONGLONG   restart_in;
 #endif
diff --git a/ext/opcache/config.m4 b/ext/opcache/config.m4
index c9fa6a7e57e4..2a83fa245597 100644
--- a/ext/opcache/config.m4
+++ b/ext/opcache/config.m4
@@ -23,8 +23,6 @@ if test "$PHP_OPCACHE" != "no"; then
   dnl Always build as shared extension
   ext_shared=yes
 
-  AC_CHECK_HEADERS([stdatomic.h])
-
   if test "$PHP_HUGE_CODE_PAGES" = "yes"; then
     AC_DEFINE(HAVE_HUGE_CODE_PAGES, 1, [Define to enable copying PHP CODE pages into HUGE PAGES (experimental)])
   fi