Fix: notifier: use store-release/load-acquire for error counter

[lttng-modules.git] / src / lttng-events.c

diff --git a/src/lttng-events.c b/src/lttng-events.c
index 3f9d0f9a91fdf7b50b7a647d1aea55413d8412b0..bcb817e55cf721490c4e6f4656b8f7626e9a9ebb 100644 (file)
--- a/src/lttng-events.c
+++ b/src/lttng-events.c
@@ -412,6 +412,7 @@ void lttng_event_notifier_group_destroy(
 
        if (event_notifier_group->error_counter) {
                struct lttng_counter *error_counter = event_notifier_group->error_counter;
+
                error_counter->ops->counter_destroy(error_counter->counter);
                module_put(error_counter->transport->owner);
                lttng_kvfree(error_counter);
@@ -1071,6 +1072,7 @@ struct lttng_event_notifier *_lttng_event_notifier_create(
                void *filter, enum lttng_kernel_instrumentation itype)
 {
        struct lttng_event_notifier *event_notifier;
+       struct lttng_counter *error_counter;
        const char *event_name;
        struct hlist_head *head;
        int ret;
@@ -1234,9 +1236,12 @@ struct lttng_event_notifier *_lttng_event_notifier_create(
 
        /*
         * Clear the error counter bucket. The sessiond keeps track of which
-        * bucket is currently in use. We trust it.
+        * bucket is currently in use. We trust it. The session lock
+        * synchronizes against concurrent creation of the error
+        * counter.
         */
-       if (event_notifier_group->error_counter) {
+       error_counter = event_notifier_group->error_counter;
+       if (error_counter) {
                size_t dimension_index[1];
 
                /*
@@ -1250,9 +1255,7 @@ struct lttng_event_notifier *_lttng_event_notifier_create(
                }
 
                dimension_index[0] = event_notifier->error_counter_index;
-               ret = event_notifier_group->error_counter->ops->counter_clear(
-                               event_notifier_group->error_counter->counter,
-                               dimension_index);
+               ret = error_counter->ops->counter_clear(error_counter->counter, dimension_index);
                if (ret) {
                        printk(KERN_INFO "LTTng: event_notifier: Unable to clear error counter bucket %llu\n",
                                event_notifier->error_counter_index);