Move caller back to zend_fiber

Caller is specific to treating fibers as a stack, so keep it with that implementation. If an implementation jumped between fibers, caller can be misleading or inaccurate.

Author: trowski

Zend/zend_fibers.c

@@ -240,18 +240,11 @@ ZEND_API zend_fiber_context *zend_fiber_switch_context(zend_fiber_context *to)
 	zend_fiber_capture_vm_state(&state);
 
 	to->status = ZEND_FIBER_STATUS_RUNNING;
-	if (to->caller == NULL) {
-		to->caller = from;
-	}
 
 	if (from->status == ZEND_FIBER_STATUS_RUNNING) {
 		from->status = ZEND_FIBER_STATUS_SUSPENDED;
 	}
 
-	if (from->caller == to) {
-		from->caller = NULL;
-	}
-
 	EG(current_fiber) = to;
 
 #ifdef __SANITIZE_ADDRESS__
@@ -353,7 +346,10 @@ static ZEND_STACK_ALIGNED zend_fiber_context *zend_fiber_execute(zend_fiber_cont
 	fiber->execute_data = NULL;
 	fiber->stack_bottom = NULL;
 
-	return fiber->caller;
+	zend_fiber_context *caller = fiber->caller;
+	fiber->caller = NULL;
+
+	return caller;
 }
 
 static zend_object *zend_fiber_object_create(zend_class_entry *ce)
@@ -380,6 +376,7 @@ static void zend_fiber_object_destroy(zend_object *object)
 	zend_object *exception = EG(exception);
 	EG(exception) = NULL;
 
+	fiber->caller = EG(current_fiber);
 	fiber->flags |= ZEND_FIBER_FLAG_DESTROYED;
 
 	zend_fiber_switch_context(zend_fiber_get_context(fiber));
@@ -452,6 +449,8 @@ ZEND_METHOD(Fiber, start)
 		RETURN_THROWS();
 	}
 
+	fiber->caller = EG(current_fiber);
+
 	zend_fiber_switch_context(context);
 
 	if (fiber->status == ZEND_FIBER_STATUS_DEAD) {
@@ -477,24 +476,27 @@ ZEND_METHOD(Fiber, suspend)
 	}
 
 	zend_fiber *fiber = zend_fiber_from_context(EG(current_fiber));
+	zend_fiber_context *caller = fiber->caller;
 
 	if (UNEXPECTED(fiber->flags & ZEND_FIBER_FLAG_DESTROYED)) {
 		zend_throw_error(zend_ce_fiber_error, "Cannot suspend in a force-closed fiber");
 		RETURN_THROWS();
 	}
 
 	ZEND_ASSERT(fiber->status == ZEND_FIBER_STATUS_RUNNING);
+	ZEND_ASSERT(caller != NULL);
 
 	if (value) {
 		ZVAL_COPY(&fiber->value, value);
 	} else {
 		ZVAL_NULL(&fiber->value);
 	}
 
+	fiber->caller = NULL;
 	fiber->execute_data = EG(current_execute_data);
 	fiber->stack_bottom->prev_execute_data = NULL;
 
-	zend_fiber_switch_context(fiber->caller);
+	zend_fiber_switch_context(caller);
 
 	if (fiber->flags & ZEND_FIBER_FLAG_DESTROYED) {
 		// This occurs when the fiber is GC'ed while suspended.
@@ -537,6 +539,7 @@ ZEND_METHOD(Fiber, resume)
 		ZVAL_NULL(&fiber->value);
 	}
 
+	fiber->caller = EG(current_fiber);
 	fiber->stack_bottom->prev_execute_data = EG(current_execute_data);
 
 	zend_fiber_switch_context(zend_fiber_get_context(fiber));
@@ -568,6 +571,7 @@ ZEND_METHOD(Fiber, throw)
 	Z_ADDREF_P(exception);
 	fiber->exception = exception;
 
+	fiber->caller = EG(current_fiber);
 	fiber->stack_bottom->prev_execute_data = EG(current_execute_data);
 
 	zend_fiber_switch_context(zend_fiber_get_context(fiber));
@@ -693,7 +697,6 @@ void zend_fiber_init(void)
 	zend_fiber_context *context = ecalloc(1, sizeof(zend_fiber_context));
 
 	context->status = ZEND_FIBER_STATUS_RUNNING;
-	context->caller = (zend_fiber_context *) -1;
 
 	EG(main_fiber) = context;
 	EG(current_fiber) = context;

Zend/zend_fibers.h

@@ -76,7 +76,6 @@ typedef zend_fiber_context *(*zend_fiber_coroutine)(zend_fiber_context *context)
 	void *handle; \
 	/* Pointer that identifies the fiber type. */ \
 	void *kind; \
-	zend_fiber_context *caller; \
 	zend_fiber_coroutine function; \
 	zend_fiber_stack stack; \
 	zend_fiber_status status; \
@@ -106,6 +105,9 @@ struct _zend_fiber {
 	/* Fiber context fields (embedded to avoid memory allocation). */
 	ZEND_FIBER_CONTEXT_FIELDS;
 
+	/* Fiber that resumed us. */
+	zend_fiber_context *caller;
+
 	/* Callback and info / cache to be used when fiber is started. */
 	zend_fcall_info fci;
 	zend_fcall_info_cache fci_cache;

ext/zend_test/test.c

@@ -436,7 +436,12 @@ static void fiber_enter_observer(zend_fiber_context *from, zend_fiber_context *t
 	if (ZT_G(observer_fiber_switch)) {
 		if (to->status == ZEND_FIBER_STATUS_INIT) {
 			php_printf("<init '%p'>\n", to);
-		} else if (to->caller == NULL) {
+		} else if (to != EG(main_fiber)) {
+			zend_fiber *fiber = zend_fiber_from_context(to);
+			if (fiber->caller != from) {
+				return;
+			}
+
 			if (to->flags & ZEND_FIBER_FLAG_DESTROYED) {
 				php_printf("<destroying '%p'>\n", to);
 			} else if (to->status != ZEND_FIBER_STATUS_DEAD) {
@@ -449,16 +454,19 @@ static void fiber_enter_observer(zend_fiber_context *from, zend_fiber_context *t
 static void fiber_suspend_observer(zend_fiber_context *from, zend_fiber_context *to)
 {
 	if (ZT_G(observer_fiber_switch)) {
-		if (from->caller == to && from->status == ZEND_FIBER_STATUS_RUNNING) {
-			php_printf("<suspend '%p'>\n", from);
-		} else if (from->status == ZEND_FIBER_STATUS_DEAD) {
+		if (from->status == ZEND_FIBER_STATUS_DEAD) {
 			if (from->flags & ZEND_FIBER_FLAG_THREW) {
 				php_printf("<threw '%p'>\n", from);
 			} else if (from->flags & ZEND_FIBER_FLAG_DESTROYED) {
 				php_printf("<destroyed '%p'>\n", from);
 			} else {
 				php_printf("<returned '%p'>\n", from);
 			}
+		} else if (from != EG(main_fiber)) {
+			zend_fiber *fiber = zend_fiber_from_context(from);
+			if (fiber->caller == NULL) {
+				php_printf("<suspend '%p'>\n", from);
+			}
 		}
 	}
 }