baddr: get session under lock

[lttng-ust.git] / liblttng-ust / lttng-ust-comm.c

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index 77d8e3fcb3564de19100b0a50c080ecba5ba2ad4..256cbdc625ef19f6da306124542a6e0a08ab593f 100644 (file)
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -52,6 +52,7 @@
 #include "lttng-tracer-core.h"
 #include "compat.h"
 #include "../libringbuffer/tlsfixup.h"
+#include "lttng-ust-baddr.h"
 
 /*
  * Has lttng ust comm constructor been called ?
@@ -107,7 +108,8 @@ struct sock_info {
 
        char wait_shm_path[PATH_MAX];
        char *wait_shm_mmap;
-       struct lttng_session *session_enabled;
+       /* Keep track of lazy state dump not performed yet. */
+       int statedump_pending;
 };
 
 /* Socket from app (connect) to session daemon (listen) for communication */
@@ -125,7 +127,7 @@ struct sock_info global_apps = {
 
        .wait_shm_path = "/" LTTNG_UST_WAIT_FILENAME,
 
-       .session_enabled = NULL,
+       .statedump_pending = 0,
 };
 
 /* TODO: allow global_apps_sock_path override */
@@ -140,7 +142,7 @@ struct sock_info local_apps = {
        .socket = -1,
        .notify_socket = -1,
 
-       .session_enabled = NULL,
+       .statedump_pending = 0,
 };
 
 static int wait_poll_fallback;
@@ -183,7 +185,6 @@ static const char *cmd_name_mapping[] = {
 
 static const char *str_timeout;
 static int got_timeout_env;
-static void *ust_baddr_handle;
 
 extern void lttng_ring_buffer_client_overwrite_init(void);
 extern void lttng_ring_buffer_client_overwrite_rt_init(void);
@@ -242,39 +243,6 @@ void print_cmd(int cmd, int handle)
                lttng_ust_obj_get_name(handle), handle);
 }
 
-static
-void *lttng_ust_baddr_handle(void)
-{
-       if (!ust_baddr_handle) {
-               ust_baddr_handle = dlopen(
-                       "liblttng-ust-baddr.so.0", RTLD_NOW | RTLD_GLOBAL);
-               if (ust_baddr_handle == NULL)
-                       ERR("%s", dlerror());
-       }
-       return ust_baddr_handle;
-}
-
-static
-int lttng_ust_baddr_statedump(struct lttng_session *session)
-{
-       static
-       int (*lttng_ust_baddr_init_fn)(struct lttng_session *);
-
-       if (!lttng_ust_baddr_init_fn) {
-               void *baddr_handle = lttng_ust_baddr_handle();
-               if (baddr_handle) {
-                       lttng_ust_baddr_init_fn = dlsym(baddr_handle,
-                               "lttng_ust_baddr_statedump");
-                       if (lttng_ust_baddr_init_fn == NULL)
-                               ERR("%s", dlerror());
-               }
-               if (!lttng_ust_baddr_init_fn)
-                       return -1;
-       }
-
-       return lttng_ust_baddr_init_fn(session);
-}
-
 static
 int setup_local_apps(void)
 {
@@ -420,6 +388,28 @@ int handle_register_done(struct sock_info *sock_info)
        return 0;
 }
 
+/*
+ * Only execute pending statedump after the constructor semaphore has
+ * been posted by each listener thread. This means statedump will only
+ * be performed after the "registration done" command is received from
+ * each session daemon the application is connected to.
+ *
+ * This ensures we don't run into deadlock issues with the dynamic
+ * loader mutex, which is held while the constructor is called and
+ * waiting on the constructor semaphore. All operations requiring this
+ * dynamic loader lock need to be postponed using this mechanism.
+ */
+static
+void handle_pending_statedump(struct sock_info *sock_info)
+{
+       int ctor_passed = sock_info->constructor_sem_posted;
+
+       if (ctor_passed && sock_info->statedump_pending) {
+               sock_info->statedump_pending = 0;
+               lttng_handle_pending_statedump(sock_info);
+       }
+}
+
 static
 int handle_message(struct sock_info *sock_info,
                int sock, struct ustcomm_ust_msg *lum)
@@ -738,6 +728,14 @@ end:
 
 error:
        ust_unlock();
+
+       /*
+        * Performed delayed statedump operations outside of the UST
+        * lock. We need to take the dynamic loader lock before we take
+        * the UST lock internally within handle_pending_statedump().
+         */
+       handle_pending_statedump(sock_info);
+
        return ret;
 }
 
@@ -1246,13 +1244,6 @@ restart:
                        ret = handle_message(sock_info, sock, &lum);
                        if (ret) {
                                ERR("Error handling message for %s socket", sock_info->name);
-                       } else {
-                               struct lttng_session *session =
-                                       sock_info->session_enabled;
-                               if (session) {
-                                       sock_info->session_enabled = NULL;
-                                       lttng_ust_baddr_statedump(session);
-                               }
                        }
                        continue;
                default:
@@ -1489,12 +1480,6 @@ void __attribute__((destructor)) lttng_ust_exit(void)
         * cleanup the threads if there are stalled in a syscall.
         */
        lttng_ust_cleanup(1);
-
-       if (ust_baddr_handle) {
-               int ret = dlclose(ust_baddr_handle);
-               if (ret)
-                       ERR("%s", dlerror());
-       }
 }
 
 /*
@@ -1573,9 +1558,8 @@ void ust_after_fork_child(sigset_t *restore_sigset)
        lttng_ust_init();
 }
 
-void lttng_ust_sockinfo_session_enabled(void *owner,
-               struct lttng_session *session_enabled)
+void lttng_ust_sockinfo_session_enabled(void *owner)
 {
        struct sock_info *sock_info = owner;
-       sock_info->session_enabled = session_enabled;
+       sock_info->statedump_pending = 1;
 }