Clean kconsumerd spawning process

[lttng-tools.git] / ltt-sessiond / main.c

diff --git a/ltt-sessiond/main.c b/ltt-sessiond/main.c
index 5337d6df44781980c7cc77fd4211932fcf540de0..9fd5c1c75f2684489713d5c83131ad8a406f85cb 100644 (file)
--- a/ltt-sessiond/main.c
+++ b/ltt-sessiond/main.c
@@ -477,12 +477,12 @@ error:
 }
 
 /*
- *  start_kconsumerd_thread
+ *  spawn_kconsumerd_thread
  *
  *  Start the thread_manage_kconsumerd. This must be done after a kconsumerd
  *  exec or it will fails.
  */
-static int start_kconsumerd_thread(void)
+static int spawn_kconsumerd_thread(void)
 {
        int ret;
 
@@ -495,6 +495,7 @@ static int start_kconsumerd_thread(void)
                goto error;
        }
 
+       /* Wait for the kconsumerd thread to be ready */
        sem_wait(&kconsumerd_sem);
 
        return 0;
@@ -504,13 +505,17 @@ error:
 }
 
 /*
- *  kernel_start_consumer
+ *  spawn_kconsumerd
  *
- *  Start a kernel consumer daemon (kconsumerd).
+ *  Fork and exec a kernel consumer daemon (kconsumerd).
+ *
+ *  NOTE: It is very important to fork a kconsumerd BEFORE opening any kernel
+ *  file descriptor using the libkernelctl or kernel-ctl functions. So, a
+ *  kernel consumer MUST only be spawned before creating a kernel session.
  *
  *  Return pid if successful else -1.
  */
-pid_t kernel_start_consumer(void)
+static pid_t spawn_kconsumerd(void)
 {
        int ret;
        pid_t pid;
@@ -538,6 +543,47 @@ error:
        return ret;
 }
 
+/*
+ *  start_kconsumerd
+ *
+ *  Spawn the kconsumerd daemon and session daemon thread.
+ */
+static int start_kconsumerd(void)
+{
+       int ret;
+
+       DBG("Spawning kconsumerd");
+
+       pthread_mutex_lock(&kconsumerd_pid_mutex);
+       if (kconsumerd_pid == 0) {
+               ret = spawn_kconsumerd();
+               if (ret < 0) {
+                       ERR("Spawning kconsumerd failed");
+                       ret = LTTCOMM_KERN_CONSUMER_FAIL;
+                       pthread_mutex_unlock(&kconsumerd_pid_mutex);
+                       goto error;
+               }
+
+               /* Setting up the global kconsumerd_pid */
+               kconsumerd_pid = ret;
+       }
+       pthread_mutex_unlock(&kconsumerd_pid_mutex);
+
+       DBG("Spawning kconsumerd thread");
+
+       ret = spawn_kconsumerd_thread();
+       if (ret < 0) {
+               ERR("Fatal error spawning kconsumerd thread");
+               ret = LTTCOMM_FATAL;
+               goto error;
+       }
+
+       return 0;
+
+error:
+       return ret;
+}
+
 /*
  *  send_kconsumerd_fds
  *
@@ -695,26 +741,8 @@ static int process_client_msg(struct command_ctx *cmd_ctx)
                        goto setup_error;
                }
 
-               DBG("Checking if kconsumerd is alive");
-               pthread_mutex_lock(&kconsumerd_pid_mutex);
-               if (kconsumerd_pid == 0) {
-                       ret = kernel_start_consumer();
-                       if (ret < 0) {
-                               ERR("Kernel start kconsumerd failed");
-                               ret = LTTCOMM_KERN_CONSUMER_FAIL;
-                               pthread_mutex_unlock(&kconsumerd_pid_mutex);
-                               goto error;
-                       }
-
-                       /* Setting up the global kconsumerd_pid */
-                       kconsumerd_pid = ret;
-               }
-               pthread_mutex_unlock(&kconsumerd_pid_mutex);
-
-               ret = start_kconsumerd_thread();
+               ret = start_kconsumerd();
                if (ret < 0) {
-                       ERR("Fatal error : start_kconsumerd_thread()");
-                       ret = LTTCOMM_FATAL;
                        goto error;
                }