lvmlockd: client mutex ordering

Avoid deadlock between threads on mutexes (in theory.)

diff --git a/daemons/lvmlockd/lvmlockd-core.c b/daemons/lvmlockd/lvmlockd-core.c
index 887226f1a74292464303bff4bde2ef1d0ab553ad..1261f648205dbad5fa962bd6107a8251b8fe19f9 100644 (file)
--- a/daemons/lvmlockd/lvmlockd-core.c
+++ b/daemons/lvmlockd/lvmlockd-core.c
@@ -4690,9 +4690,12 @@ static int dump_info(int *dump_len)
 
        /*
         * clients
+        * Proper lock order is client_mutex then cl->mutex,
+        * but cl->mutex is already held so skip client info
+        * if it would block.
         */
-
-       pthread_mutex_lock(&client_mutex);
+       if (pthread_mutex_trylock(&client_mutex))
+               goto print_ls;
        list_for_each_entry(cl, &client_list, list) {
                ret = print_client(cl, "client", pos, len);
                if (ret >= len - pos) {
@@ -4706,6 +4709,7 @@ static int dump_info(int *dump_len)
        if (rv < 0)
                return rv;
 
+ print_ls:
        /*
         * lockspaces with their action/resource/lock info
         */