libxl: suspend: Async domain_suspend_callback_common

Make domain_suspend_callback_common do its work and then call
dss->callback_common_done, rather than simply returning its answer.

This is preparatory to abolishing the usleeps in this function and
replacing them with use of the event machinery.

No functional change.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

---
v3: Remove some trailing whitespace

tools/libxl/libxl_dom.c

@@ -755,6 +755,10 @@ int libxl__toolstack_restore(uint32_t domid, const uint8_t *buf,
 
 static void domain_suspend_done(libxl__egc *egc,
                         libxl__domain_suspend_state *dss, int rc);
+static void domain_suspend_callback_common_done(libxl__egc *egc,
+                                libxl__domain_suspend_state *dss, int ok);
+static void remus_domain_suspend_callback_common_done(libxl__egc *egc,
+                                libxl__domain_suspend_state *dss, int ok);
 
 /*----- complicated callback, called by xc_domain_save -----*/
 
@@ -1020,7 +1024,9 @@ int libxl__domain_resume_device_model(libxl__gc *gc, uint32_t domid)
     return 0;
 }
 
-int libxl__domain_suspend_callback_common(libxl__domain_suspend_state *dss)
+/* calls dss->callback_common_done when done */
+static void domain_suspend_callback_common(libxl__egc *egc,
+                                           libxl__domain_suspend_state *dss)
 {
     STATE_AO_GC(dss->ao);
     unsigned long hvm_s_state = 0, hvm_pvdrv = 0;
@@ -1043,12 +1049,12 @@ int libxl__domain_suspend_callback_common(libxl__domain_suspend_state *dss)
         ret = xc_evtchn_notify(dss->xce, dss->suspend_eventchn);
         if (ret < 0) {
             LOG(ERROR, "xc_evtchn_notify failed ret=%d", ret);
-            return 0;
+            goto err;
         }
         ret = xc_await_suspend(CTX->xch, dss->xce, dss->suspend_eventchn);
         if (ret < 0) {
             LOG(ERROR, "xc_await_suspend failed ret=%d", ret);
-            return 0;
+            goto err;
         }
         dss->guest_responded = 1;
         goto guest_suspended;
@@ -1059,7 +1065,7 @@ int libxl__domain_suspend_callback_common(libxl__domain_suspend_state *dss)
         ret = xc_domain_shutdown(CTX->xch, domid, SHUTDOWN_suspend);
         if (ret < 0) {
             LOGE(ERROR, "xc_domain_shutdown failed");
-            return 0;
+            goto err;
         }
         /* The guest does not (need to) respond to this sort of request. */
         dss->guest_responded = 1;
@@ -1113,7 +1119,7 @@ int libxl__domain_suspend_callback_common(libxl__domain_suspend_state *dss)
          */
         if (!strcmp(state, "suspend")) {
             LOG(ERROR, "guest didn't acknowledge suspend, request cancelled");
-            return 0;
+            goto err;
         }
 
         LOG(DEBUG, "guest acknowledged suspend request");
@@ -1143,17 +1149,19 @@ int libxl__domain_suspend_callback_common(libxl__domain_suspend_state *dss)
     }
 
     LOG(ERROR, "guest did not suspend");
-    return 0;
+ err:
+    dss->callback_common_done(egc, dss, 0);
+    return;
 
  guest_suspended:
     if (dss->hvm) {
         ret = libxl__domain_suspend_device_model(gc, dss);
         if (ret) {
             LOG(ERROR, "libxl__domain_suspend_device_model failed ret=%d", ret);
-            return 0;
+            goto err;
         }
     }
-    return 1;
+    dss->callback_common_done(egc, dss, 1);
 }
 
 static inline char *physmap_path(libxl__gc *gc, uint32_t domid,
@@ -1246,8 +1254,14 @@ static void libxl__domain_suspend_callback(void *data)
     libxl__egc *egc = shs->egc;
     libxl__domain_suspend_state *dss = CONTAINER_OF(shs, *dss, shs);
 
-    int ok = libxl__domain_suspend_callback_common(dss);
-    libxl__xc_domain_saverestore_async_callback_done(egc, shs, ok);
+    dss->callback_common_done = domain_suspend_callback_common_done;
+    domain_suspend_callback_common(egc, dss);
+}
+
+static void domain_suspend_callback_common_done(libxl__egc *egc,
+                                libxl__domain_suspend_state *dss, int ok)
+{
+    libxl__xc_domain_saverestore_async_callback_done(egc, &dss->shs, ok);
 }
 
 /*----- remus callbacks -----*/
@@ -1258,9 +1272,15 @@ static void libxl__remus_domain_suspend_callback(void *data)
     libxl__egc *egc = shs->egc;
     libxl__domain_suspend_state *dss = CONTAINER_OF(shs, *dss, shs);
 
+    dss->callback_common_done = remus_domain_suspend_callback_common_done;
+    domain_suspend_callback_common(egc, dss);
+}
+
+static void remus_domain_suspend_callback_common_done(libxl__egc *egc,
+                                libxl__domain_suspend_state *dss, int ok)
+{
     /* REMUS TODO: Issue disk and network checkpoint reqs. */
-    int ok = libxl__domain_suspend_callback_common(dss);
-    libxl__xc_domain_saverestore_async_callback_done(egc, shs, ok);
+    libxl__xc_domain_saverestore_async_callback_done(egc, &dss->shs, ok);
 }
 
 static int libxl__remus_domain_resume_callback(void *data)

tools/libxl/libxl_internal.h

@@ -2447,6 +2447,8 @@ struct libxl__domain_suspend_state {
     int interval; /* checkpoint interval (for Remus) */
     libxl__save_helper_state shs;
     libxl__logdirty_switch logdirty;
+    void (*callback_common_done)(libxl__egc*,
+                                 struct libxl__domain_suspend_state*, int ok);
     /* private for libxl__domain_save_device_model */
     libxl__save_device_model_cb *save_dm_callback;
     libxl__datacopier_state save_dm_datacopier;
@@ -2739,7 +2741,7 @@ _hidden void libxl__xc_domain_save_done(libxl__egc*, void *dss_void,
 void libxl__xc_domain_saverestore_async_callback_done(libxl__egc *egc,
                            libxl__save_helper_state *shs, int return_value);
 
-_hidden int libxl__domain_suspend_callback_common(libxl__domain_suspend_state*);
+
 _hidden void libxl__domain_suspend_common_switch_qemu_logdirty
                                (int domid, unsigned int enable, void *data);
 _hidden int libxl__toolstack_save(uint32_t domid, uint8_t **buf,