Fix: Synchronization issue for data available command

[lttng-tools.git] / src / common / kernel-consumer / kernel-consumer.c

diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c
index 2456d3fc91936c69f074bbd038ee227c46e48220..196deee9a153e521447703915d9ee9d2790502a4 100644 (file)
--- a/src/common/kernel-consumer/kernel-consumer.c
+++ b/src/common/kernel-consumer/kernel-consumer.c
@@ -282,8 +282,19 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
        }
        case LTTNG_CONSUMER_DATA_AVAILABLE:
        {
-               rcu_read_unlock();
-               return -ENOSYS;
+               int32_t ret;
+               uint64_t id = msg.u.data_available.session_id;
+
+               DBG("Kernel consumer data available command for id %" PRIu64, id);
+
+               ret = consumer_data_available(id);
+
+               /* Send back returned value to session daemon */
+               ret = lttcomm_send_unix_sock(sock, &ret, sizeof(ret));
+               if (ret < 0) {
+                       PERROR("send data available ret code");
+               }
+               break;
        }
        default:
                goto end_nosignal;
@@ -472,3 +483,31 @@ error:
        return ret;
 }
 
+/*
+ * Check if data is still being extracted from the buffers for a specific
+ * stream. Consumer data lock MUST be acquired before calling this function
+ * and the stream lock.
+ *
+ * Return 0 if the traced data are still getting read else 1 meaning that the
+ * data is available for trace viewer reading.
+ */
+int lttng_kconsumer_data_available(struct lttng_consumer_stream *stream)
+{
+       int ret;
+
+       assert(stream);
+
+       ret = kernctl_get_next_subbuf(stream->wait_fd);
+       if (ret == 0) {
+               /* There is still data so let's put back this subbuffer. */
+               ret = kernctl_put_subbuf(stream->wait_fd);
+               assert(ret == 0);
+               goto end;
+       }
+
+       /* Data is available to be read for this stream. */
+       ret = 1;
+
+end:
+       return ret;
+}