Fix: health subsystem issues with shared code
[lttng-tools.git] / src / bin / lttng-sessiond / health.c
index d382c04b536cc060fba5cb181e5e156696264924..b36ddc4a337b6bc6c5aa389d45c004a0c3be9580 100644 (file)
@@ -32,6 +32,45 @@ static const struct timespec time_delta = {
        .tv_nsec = DEFAULT_HEALTH_CHECK_DELTA_NS,
 };
 
+/* Define TLS health state. */
+DEFINE_URCU_TLS(struct health_state, health_state);
+
+/*
+ * It ensures that TLS memory used for the node and its container structure
+ * don't get reclaimed after the TLS owner thread exits until we have finished
+ * using it.
+ */
+static pthread_mutex_t health_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+static struct health_tls_state_list health_state_list = {
+       .head = CDS_LIST_HEAD_INIT(health_state_list.head),
+};
+
+/*
+ * This keeps track of the error state for unregistered thread. A thread
+ * reporting a health error, normally unregisters and quits. This makes the TLS
+ * health state not available to the health_check_state() call so on unregister
+ * we update this global error array so we can keep track of which thread was
+ * on error if the TLS health state has been removed.
+ */
+static enum health_flags global_error_state[HEALTH_NUM_TYPE];
+
+/*
+ * Lock health state global list mutex.
+ */
+static void state_lock(void)
+{
+       pthread_mutex_lock(&health_mutex);
+}
+
+/*
+ * Unlock health state global list mutex.
+ */
+static void state_unlock(void)
+{
+       pthread_mutex_unlock(&health_mutex);
+}
+
 /*
  * Set time difference in res from time_a and time_b.
  */
@@ -68,17 +107,51 @@ static int time_diff_gt(const struct timespec *time_a,
 }
 
 /*
- * Check health of a specific health state counter.
+ * Health mutex MUST be held across use of the returned struct health_state to
+ * provide existence guarantee.
+ *
+ * Return the health_state object or NULL if not found.
+ */
+static struct health_state *find_health_state(enum health_type type)
+{
+       struct health_state *state;
+
+       /* Find the right health state in the global TLS list. */
+       cds_list_for_each_entry(state, &health_state_list.head, node) {
+               if (state->type == type) {
+                       return state;
+               }
+       }
+
+       return NULL;
+}
+
+/*
+ * Check health of a specific health type. Note that if a thread has not yet
+ * initialize its health subsystem or has quit, it's considered in a good
+ * state.
  *
  * Return 0 if health is bad or else 1.
  */
-int health_check_state(struct health_state *state)
+int health_check_state(enum health_type type)
 {
        int retval = 1, ret;
        unsigned long current, last;
        struct timespec current_time;
+       struct health_state *state;
+
+       assert(type < HEALTH_NUM_TYPE);
 
-       assert(state);
+       state_lock();
+
+       state = find_health_state(type);
+       if (!state) {
+               /* Check the global state since the state is not visiable anymore. */
+               if (global_error_state[type] & HEALTH_ERROR) {
+                       retval = 0;
+               }
+               goto not_found;
+       }
 
        last = state->last;
        current = uatomic_read(&state->current);
@@ -125,6 +198,56 @@ int health_check_state(struct health_state *state)
 end:
        DBG("Health state current %lu, last %lu, ret %d",
                        current, last, ret);
+not_found:
+       state_unlock();
 
        return retval;
 }
+
+/*
+ * Init health state.
+ */
+void health_register(enum health_type type)
+{
+       struct health_state *state;
+
+       assert(type < HEALTH_NUM_TYPE);
+
+       /* Init TLS state. */
+       uatomic_set(&URCU_TLS(health_state).last, 0);
+       uatomic_set(&URCU_TLS(health_state).last_time.tv_sec, 0);
+       uatomic_set(&URCU_TLS(health_state).last_time.tv_nsec, 0);
+       uatomic_set(&URCU_TLS(health_state).current, 0);
+       uatomic_set(&URCU_TLS(health_state).flags, 0);
+       uatomic_set(&URCU_TLS(health_state).type, type);
+
+       /* Add it to the global TLS state list. */
+       state_lock();
+       state = find_health_state(type);
+       /*
+        * Duplicates are not accepted, since lookups don't handle them at the
+        * moment.
+        */
+       assert(!state);
+
+       cds_list_add(&URCU_TLS(health_state).node, &health_state_list.head);
+       state_unlock();
+}
+
+/*
+ * Remove node from global list.
+ */
+void health_unregister(void)
+{
+       state_lock();
+       /*
+        * On error, set the global_error_state since we are about to remove
+        * the node from the global list.
+        */
+       if (uatomic_read(&URCU_TLS(health_state).flags) & HEALTH_ERROR) {
+               uatomic_set(&global_error_state[URCU_TLS(health_state).type],
+                               HEALTH_ERROR);
+       }
+       cds_list_del(&URCU_TLS(health_state).node);
+       state_unlock();
+}
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