Fix: handle concurrent flush vs get_next_subbuf on metadata cache

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

diff --git a/lttng-events.c b/lttng-events.c
index f47e9dcfcebbf9f62c488eac3b339e0d497c1499..98992f9f7943047f967233edffb4083df39585b8 100644 (file)
--- a/lttng-events.c
+++ b/lttng-events.c
@@ -519,7 +519,7 @@ int _lttng_event_unregister(struct lttng_event *event)
 
        switch (event->instrumentation) {
        case LTTNG_KERNEL_TRACEPOINT:
-               ret = kabi_2635_tracepoint_probe_unregister(event->desc->name,
+               ret = kabi_2635_tracepoint_probe_unregister(event->desc->kname,
                                                  event->desc->probe_callback,
                                                  event);
                if (ret)
@@ -597,16 +597,20 @@ int lttng_metadata_output_channel(struct lttng_metadata_stream *stream,
 
        /*
         * Ensure we support mutiple get_next / put sequences followed
-        * by put_next.
+        * by put_next. The metadata stream lock internally protects
+        * reading the metadata cache. It can indeed be read
+        * concurrently by "get_next_subbuf" and "flush" operations on
+        * the buffer invoked by different processes.
         */
+       mutex_lock(&stream->lock);
        WARN_ON(stream->metadata_in < stream->metadata_out);
        if (stream->metadata_in != stream->metadata_out)
-               return 0;
+               goto end;
 
        len = stream->metadata_cache->metadata_written -
                stream->metadata_in;
        if (!len)
-               return 0;
+               goto end;
        reserve_len = min_t(size_t,
                        stream->transport->ops.packet_avail_size(chan),
                        len);
@@ -628,6 +632,7 @@ int lttng_metadata_output_channel(struct lttng_metadata_stream *stream,
        ret = reserve_len;
 
 end:
+       mutex_unlock(&stream->lock);
        return ret;
 }
 
@@ -1286,4 +1291,5 @@ MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 MODULE_DESCRIPTION("LTTng Events");
 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
        __stringify(LTTNG_MODULES_MINOR_VERSION) "."
-       __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION));
+       __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
+       LTTNG_MODULES_EXTRAVERSION);