[Xen-changelog] [xen-unstable] xenstore: Make sure that libxs reports an error if xenstored drops

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1274944826 -3600
# Node ID 5be2d2a7f445bab61617b09627ca7f6a8ec90a69
# Parent  22ecd71786082c8361f019a5e6f41b8f8a752c8b
xenstore: Make sure that libxs reports an error if xenstored drops
the connection, rather than getting stuck forever.

Patch from: Steven Smith <steven.smith@xxxxxxxxxxxxx>
Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
---
 tools/xenstore/xs.c |   36 +++++++++++++++++++++++++++++++++---
 1 files changed, 33 insertions(+), 3 deletions(-)

diff -r 22ecd7178608 -r 5be2d2a7f445 tools/xenstore/xs.c
--- a/tools/xenstore/xs.c       Thu May 27 08:19:47 2010 +0100
+++ b/tools/xenstore/xs.c       Thu May 27 08:20:26 2010 +0100
@@ -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
        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

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