xenstore: Make sure that libxs reports an error if xenstored drops

the connection, rather than getting stuck forever.

Patch from: Steven Smith <steven.smith@eu.citrix.com>
Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>

diff --git a/tools/xenstore/xs.c b/tools/xenstore/xs.c
index 7e3d9c4b6357e78aa35e9e02ce189afbf382530d..094db25efafd352e7a02a1d592dbe8a43d84665e 100644 (file)
--- a/tools/xenstore/xs.c
+++ b/tools/xenstore/xs.c
@@ -94,6 +94,8 @@ struct xs_handle {
  */
 #define cleanup_pop(run)        ((void)0); pthread_cleanup_pop(run)
 
+#define read_thread_exists(h)  (h->read_thr_exists)
+
 static void *read_thread(void *arg);
 
 #else /* !defined(USE_PTHREAD) */
@@ -112,6 +114,7 @@ struct xs_handle {
 #define condvar_wait(c,m,hnd)  read_message(hnd)
 #define cleanup_push(f, a)     ((void)0)
 #define cleanup_pop(run)       ((void)0)
+#define read_thread_exists(h)  (0)
 
 #endif
 
@@ -330,16 +333,25 @@ static void *read_reply(
 {
        struct xs_stored_msg *msg;
        char *body;
+       int read_from_thread;
+
+       read_from_thread = read_thread_exists(h);
 
 #ifdef USE_PTHREAD
        /* Read from comms channel ourselves if there is no reader thread. */
-       if (!h->read_thr_exists && (read_message(h) == -1))
+       if (!read_from_thread && (read_message(h) == -1))
                return NULL;
 #endif
 
        mutex_lock(&h->reply_mutex);
-       while (list_empty(&h->reply_list))
+       while (list_empty(&h->reply_list) && (!read_from_thread || read_thread_exists(h)))
                condvar_wait(&h->reply_condvar, &h->reply_mutex, h);
+       if (read_from_thread && !read_thread_exists(h)) {
+               mutex_unlock(&h->reply_mutex);
+               errno = EINVAL;
+               return NULL;
+       }
+       assert(!list_empty(&h->reply_list));
        msg = list_top(&h->reply_list, struct xs_stored_msg, list);
        list_del(&msg->list);
        assert(list_empty(&h->reply_list));
@@ -647,8 +659,13 @@ char **xs_read_watch(struct xs_handle *h, unsigned int *num)
        mutex_lock(&h->watch_mutex);
 
        /* Wait on the condition variable for a watch to fire. */
-       while (list_empty(&h->watch_list))
+       while (list_empty(&h->watch_list) && read_thread_exists(h))
                condvar_wait(&h->watch_condvar, &h->watch_mutex, h);
+       if (!read_thread_exists(h)) {
+               mutex_unlock(&h->watch_mutex);
+               errno = EINVAL;
+               return NULL;
+       }
        msg = list_top(&h->watch_list, struct xs_stored_msg, list);
        list_del(&msg->list);
 
@@ -944,6 +961,19 @@ static void *read_thread(void *arg)
        while (read_message(h) != -1)
                continue;
 
+       /* Kick anyone waiting for a reply */
+       pthread_mutex_lock(&h->request_mutex);
+       h->read_thr_exists = 0;
+       pthread_mutex_unlock(&h->request_mutex);
+
+       pthread_mutex_lock(&h->reply_mutex);
+       pthread_cond_signal(&h->reply_condvar);
+       pthread_mutex_unlock(&h->reply_mutex);
+
+       pthread_mutex_lock(&h->watch_mutex);
+       pthread_cond_signal(&h->watch_condvar);
+       pthread_mutex_unlock(&h->watch_mutex);
+
        return NULL;
 }
 #endif