[PATCH v2 14/16] Save/Restore Support: Add suspend/restore support for xenbus

[Bruno Alvisio <bruno.alvisio@gmail.com>]

Currently the watch path is not saved in the watch struct when it is registered.
During xenbus resume the path is needed so that the watches can be registered again.
Thus, 'path' field is added to struct watch so that watches can be re-registered
during xenbus resume.

Signed-off-by: Bruno Alvisio <bruno.alvisio@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
---
 include/xenbus.h |   2 ++
 kernel.c         |   8 +++++
 xenbus/xenbus.c  | 106 +++++++++++++++++++++++++++++++++++++++----------------
 3 files changed, 85 insertions(+), 31 deletions(-)

diff --git a/include/xenbus.h b/include/xenbus.h
index b2d5072..3871f35 100644
--- a/include/xenbus.h
+++ b/include/xenbus.h
@@ -120,6 +120,8 @@ domid_t xenbus_get_self_id(void);
 #ifdef CONFIG_XENBUS
 /* Reset the XenBus system. */
 void fini_xenbus(void);
+void suspend_xenbus(void);
+void resume_xenbus(int canceled);
 #else
 static inline void fini_xenbus(void)
 {
diff --git a/kernel.c b/kernel.c
index 933cbcd..1393d15 100644
--- a/kernel.c
+++ b/kernel.c
@@ -119,6 +119,10 @@ void start_kernel(void* par)
 
 void pre_suspend(void)
 {
+#ifdef CONFIG_XENBUS
+    suspend_xenbus();
+#endif
+
     local_irq_disable();
 
     suspend_gnttab();
@@ -139,6 +143,10 @@ void post_suspend(int canceled)
     resume_gnttab();
 
     local_irq_enable();
+
+#ifdef CONFIG_XENBUS
+    resume_xenbus(canceled);
+#endif
 }
 
 void stop_kernel(void)
diff --git a/xenbus/xenbus.c b/xenbus/xenbus.c
index c2d2bd1..d72dc3a 100644
--- a/xenbus/xenbus.c
+++ b/xenbus/xenbus.c
@@ -50,6 +50,7 @@ DECLARE_WAIT_QUEUE_HEAD(xenbus_watch_queue);
 xenbus_event_queue xenbus_events;
 static struct watch {
     char *token;
+    char *path;
     xenbus_event_queue *events;
     struct watch *next;
 } *watches;
@@ -63,6 +64,8 @@ struct xenbus_req_info
 #define NR_REQS 32
 static struct xenbus_req_info req_info[NR_REQS];
 
+static char *errmsg(struct xsd_sockmsg *rep);
+
 uint32_t xenbus_evtchn;
 
 #ifdef CONFIG_PARAVIRT
@@ -231,45 +234,39 @@ static void xenbus_thread_func(void *ign)
     struct xsd_sockmsg msg;
     unsigned prod = xenstore_buf->rsp_prod;
 
-    for (;;) 
-    {
+    for (;;) {
         wait_event(xb_waitq, prod != xenstore_buf->rsp_prod);
-        while (1) 
-        {
+        while (1) {
             prod = xenstore_buf->rsp_prod;
             DEBUG("Rsp_cons %d, rsp_prod %d.\n", xenstore_buf->rsp_cons,
-                    xenstore_buf->rsp_prod);
+                  xenstore_buf->rsp_prod);
             if (xenstore_buf->rsp_prod - xenstore_buf->rsp_cons < sizeof(msg))
                 break;
             rmb();
-            memcpy_from_ring(xenstore_buf->rsp,
-                    &msg,
-                    MASK_XENSTORE_IDX(xenstore_buf->rsp_cons),
-                    sizeof(msg));
-            DEBUG("Msg len %d, %d avail, id %d.\n",
-                    msg.len + sizeof(msg),
-                    xenstore_buf->rsp_prod - xenstore_buf->rsp_cons,
-                    msg.req_id);
+            memcpy_from_ring(xenstore_buf->rsp, &msg,
+                             MASK_XENSTORE_IDX(xenstore_buf->rsp_cons),
+                             sizeof(msg));
+            DEBUG("Msg len %d, %d avail, id %d.\n", msg.len + sizeof(msg),
+                  xenstore_buf->rsp_prod - xenstore_buf->rsp_cons, msg.req_id);
+
             if (xenstore_buf->rsp_prod - xenstore_buf->rsp_cons <
-                    sizeof(msg) + msg.len)
+                sizeof(msg) + msg.len)
                 break;
 
             DEBUG("Message is good.\n");
 
-            if(msg.type == XS_WATCH_EVENT)
-            {
-		struct xenbus_event *event = malloc(sizeof(*event) + msg.len);
+            if (msg.type == XS_WATCH_EVENT) {
+                struct xenbus_event *event = malloc(sizeof(*event) + msg.len);
                 xenbus_event_queue *events = NULL;
-		char *data = (char*)event + sizeof(*event);
+                char *data = (char*)event + sizeof(*event);
                 struct watch *watch;
 
-                memcpy_from_ring(xenstore_buf->rsp,
-		    data,
+                memcpy_from_ring(xenstore_buf->rsp, data,
                     MASK_XENSTORE_IDX(xenstore_buf->rsp_cons + sizeof(msg)),
                     msg.len);
 
-		event->path = data;
-		event->token = event->path + strlen(event->path) + 1;
+                event->path = data;
+                event->token = event->path + strlen(event->path) + 1;
 
                 mb();
                 xenstore_buf->rsp_cons += msg.len + sizeof(msg);
@@ -288,15 +285,11 @@ static void xenbus_thread_func(void *ign)
                     printk("unexpected watch token %s\n", event->token);
                     free(event);
                 }
-            }
-
-            else
-            {
+            } else {
                 req_info[msg.req_id].reply = malloc(sizeof(msg) + msg.len);
-                memcpy_from_ring(xenstore_buf->rsp,
-                    req_info[msg.req_id].reply,
-                    MASK_XENSTORE_IDX(xenstore_buf->rsp_cons),
-                    msg.len + sizeof(msg));
+                memcpy_from_ring(xenstore_buf->rsp, req_info[msg.req_id].reply,
+                                 MASK_XENSTORE_IDX(xenstore_buf->rsp_cons),
+                                 msg.len + sizeof(msg));
                 mb();
                 xenstore_buf->rsp_cons += msg.len + sizeof(msg);
                 wake_up(&req_info[msg.req_id].waitq);
@@ -380,6 +373,55 @@ void fini_xenbus(void)
 {
 }
 
+void suspend_xenbus(void)
+{
+    /* Check for live requests and wait until they finish */
+    while (1)
+    {
+        spin_lock(&req_lock);
+        if (nr_live_reqs == 0)
+            break;
+        spin_unlock(&req_lock);
+        wait_event(req_wq, (nr_live_reqs == 0));
+    }
+
+    mask_evtchn(xenbus_evtchn);
+    xenstore_buf = NULL;
+    spin_unlock(&req_lock);
+}
+
+void resume_xenbus(int canceled)
+{
+    char *msg;
+    struct watch *watch;
+    struct write_req req[2];
+    struct xsd_sockmsg *rep;
+
+#ifdef CONFIG_PARAVIRT
+    get_xenbus(&start_info);
+#else
+    get_xenbus(0);
+#endif
+    unmask_evtchn(xenbus_evtchn);
+
+    if (!canceled) {
+        for (watch = watches; watch; watch = watch->next) {
+            req[0].data = watch->path;
+            req[0].len = strlen(watch->path) + 1;
+            req[1].data = watch->token;
+            req[1].len = strlen(watch->token) + 1;
+
+            rep = xenbus_msg_reply(XS_WATCH, XBT_NIL, req, ARRAY_SIZE(req));
+            msg = errmsg(rep);
+            if (msg)
+                xprintk("error on XS_WATCH: %s\n", msg);
+            free(rep);
+        }
+    }
+
+    notify_remote_via_evtchn(xenbus_evtchn);
+}
+
 /* Send data to xenbus.  This can block.  All of the requests are seen
    by xenbus as if sent atomically.  The header is added
    automatically, using type %type, req_id %req_id, and trans_id
@@ -501,7 +543,7 @@ static char *errmsg(struct xsd_sockmsg *rep)
     res[rep->len] = 0;
     free(rep);
     return res;
-}	
+}
 
 /* Send a debug message to xenbus.  Can block. */
 static void xenbus_debug_msg(const char *msg)
@@ -601,6 +643,7 @@ char* xenbus_watch_path_token( xenbus_transaction_t xbt, const char *path, const
         events = &xenbus_events;
 
     watch->token = strdup(token);
+    watch->path = strdup(path);
     watch->events = events;
     watch->next = watches;
     watches = watch;
@@ -636,6 +679,7 @@ char* xenbus_unwatch_path_token( xenbus_transaction_t xbt, const char *path, con
     for (prev = &watches, watch = *prev; watch; prev = &watch->next, watch = *prev)
         if (!strcmp(watch->token, token)) {
             free(watch->token);
+            free(watch->path);
             *prev = watch->next;
             free(watch);
             break;
-- 
2.3.2 (Apple Git-55)


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