libxl: suspend: Abolish usleeps in domain suspend wait

Replace the use of a loop with usleep().

Instead, use a xenstore watch and an event system timeout.  (xenstore
fires watches on @releaseDomain when a domain shuts down.)

The logic which checks for the state of the domain is unchanged, and
not ideal, but we will leave that for the next patch.

There is not intended to be any semantic change, other than to make
the algorithm properly asynchronous and the consequential waiting be
on xenstore, rather than polling.

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
    Improve commit message.
v3X: Do NOT use an xswait instead of separate watch and timeout.

diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 0c48159570bf0e2f9e42cc7788f11892163a47dd..5d6dcc4ba017df7c79d4790f338046520649f4db 100644 (file)
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -1028,8 +1028,14 @@ static void domain_suspend_common_wait_guest(libxl__egc *egc,
                                              libxl__domain_suspend_state *dss);
 static void domain_suspend_common_guest_suspended(libxl__egc *egc,
                                          libxl__domain_suspend_state *dss);
+
 static void domain_suspend_common_pvcontrol_suspending(libxl__egc *egc,
       libxl__xswait_state *xswa, int rc, const char *state);
+static void suspend_common_wait_guest_watch(libxl__egc *egc,
+      libxl__ev_xswatch *xsw, const char *watch_path, const char *event_path);
+static void suspend_common_wait_guest_timeout(libxl__egc *egc,
+      libxl__ev_time *ev, const struct timeval *requested_abs);
+
 static void domain_suspend_common_failed(libxl__egc *egc,
                                          libxl__domain_suspend_state *dss);
 static void domain_suspend_common_done(libxl__egc *egc,
@@ -1176,36 +1182,59 @@ static void domain_suspend_common_wait_guest(libxl__egc *egc,
                                              libxl__domain_suspend_state *dss)
 {
     STATE_AO_GC(dss->ao);
+    int rc;
+
+    LOG(DEBUG, "wait for the guest to suspend");
+
+    rc = libxl__ev_xswatch_register(gc, &dss->guest_watch,
+                                    suspend_common_wait_guest_watch,
+                                    "@releaseDomain");
+    if (rc) goto err;
+
+    rc = libxl__ev_time_register_rel(gc, &dss->guest_timeout,
+                                     suspend_common_wait_guest_timeout,
+                                     60*1000);
+    if (rc) goto err;
+    return;
+
+ err:
+    domain_suspend_common_failed(egc, dss);
+}
+
+static void suspend_common_wait_guest_watch(libxl__egc *egc,
+      libxl__ev_xswatch *xsw, const char *watch_path, const char *event_path)
+{
+    libxl__domain_suspend_state *dss =
+        CONTAINER_OF(xsw, *dss, guest_watch);
+    STATE_AO_GC(dss->ao);
+    xc_domaininfo_t info;
     int ret;
-    int watchdog;
 
     /* Convenience aliases */
     const uint32_t domid = dss->domid;
 
-    LOG(DEBUG, "wait for the guest to suspend");
-    watchdog = 60;
-    while (watchdog > 0) {
-        xc_domaininfo_t info;
-
-        usleep(100000);
-        ret = xc_domain_getinfolist(CTX->xch, domid, 1, &info);
-        if (ret == 1 && info.domain == domid &&
-            (info.flags & XEN_DOMINF_shutdown)) {
-            int shutdown_reason;
-
-            shutdown_reason = (info.flags >> XEN_DOMINF_shutdownshift)
-                & XEN_DOMINF_shutdownmask;
-            if (shutdown_reason == SHUTDOWN_suspend) {
-                LOG(DEBUG, "guest has suspended");
-                domain_suspend_common_guest_suspended(egc, dss);
-                return;
-            }
+    ret = xc_domain_getinfolist(CTX->xch, domid, 1, &info);
+    if (ret == 1 && info.domain == domid &&
+        (info.flags & XEN_DOMINF_shutdown)) {
+        int shutdown_reason;
+
+        shutdown_reason = (info.flags >> XEN_DOMINF_shutdownshift)
+            & XEN_DOMINF_shutdownmask;
+        if (shutdown_reason == SHUTDOWN_suspend) {
+            LOG(DEBUG, "guest has suspended");
+            domain_suspend_common_guest_suspended(egc, dss);
+            return;
         }
-
-        watchdog--;
     }
+    /* otherwise, keep waiting */
+}
 
-    LOG(ERROR, "guest did not suspend");
+static void suspend_common_wait_guest_timeout(libxl__egc *egc,
+      libxl__ev_time *ev, const struct timeval *requested_abs)
+{
+    libxl__domain_suspend_state *dss = CONTAINER_OF(ev, *dss, guest_timeout);
+    STATE_AO_GC(dss->ao);
+    LOG(ERROR, "guest did not suspend, timed out");
     domain_suspend_common_failed(egc, dss);
 }
 
@@ -1215,6 +1244,9 @@ static void domain_suspend_common_guest_suspended(libxl__egc *egc,
     STATE_AO_GC(dss->ao);
     int ret;
 
+    libxl__ev_xswatch_deregister(gc, &dss->guest_watch);
+    libxl__ev_time_deregister(gc, &dss->guest_timeout);
+
     if (dss->hvm) {
         ret = libxl__domain_suspend_device_model(gc, dss);
         if (ret) {
@@ -1238,6 +1270,8 @@ static void domain_suspend_common_done(libxl__egc *egc,
 {
     EGC_GC;
     assert(!libxl__xswait_inuse(&dss->pvcontrol));
+    libxl__ev_xswatch_deregister(gc, &dss->guest_watch);
+    libxl__ev_time_deregister(gc, &dss->guest_timeout);
     dss->callback_common_done(egc, dss, ok);
 }
 
@@ -1424,6 +1458,8 @@ void libxl__domain_suspend(libxl__egc *egc, libxl__domain_suspend_state *dss)
 
     logdirty_init(&dss->logdirty);
     libxl__xswait_init(&dss->pvcontrol);
+    libxl__ev_xswatch_init(&dss->guest_watch);
+    libxl__ev_time_init(&dss->guest_timeout);
 
     switch (type) {
     case LIBXL_DOMAIN_TYPE_HVM: {

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 479edb79624d6e6dd1cc34bc355047587b212346..a67ea3c20a7e717c73d08b37b96e50b199b49921 100644 (file)
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -2445,6 +2445,8 @@ struct libxl__domain_suspend_state {
     int xcflags;
     int guest_responded;
     libxl__xswait_state pvcontrol;
+    libxl__ev_xswatch guest_watch;
+    libxl__ev_time guest_timeout;
     const char *dm_savefile;
     int interval; /* checkpoint interval (for Remus) */
     libxl__save_helper_state shs;