libdlt: Avoid busy loop in error case of mq_receive() (#59)

To avoid busy loop due to error of mq_receive() which is called
in sub thread, 100ms sleep is added for the error case.
Error log message for mq_receive() is also corrected to have errno.

Signed-off-by: Yusuke Sato <yusuke-sato@apn.alpine.co.jp>

1 files changed, 13 insertions, 1 deletions

diff --git a/src/lib/dlt_user.c b/src/lib/dlt_user.c
index 70fb564..0530ba7 100644
--- a/src/lib/dlt_user.c
+++ b/src/lib/dlt_user.c
@@ -2771,10 +2771,22 @@ void dlt_user_trace_network_segmented_thread(void *unused)
 
                 ssize_t read = mq_receive(dlt_user.dlt_segmented_queue_read_handle, (char *)&data,
                                         sizeof(s_segmented_data * ), NULL);
+                if (read < 0)
+                {
+                    if (errno != EINTR)
+                    {
+                        dlt_vlog(LOG_WARNING, "NWTSegmented: Error while reading queue: %s\n", strerror(errno));
+                        usleep(DLT_USER_MQ_ERROR_RETRY_INTERVAL);
+                    }
+                    continue;
+                }
 
                 if(read != sizeof(s_segmented_data *))
                 {
-                    dlt_log(LOG_WARNING,"NWTSegmented: Could not send end segment.\n");
+                    // This case will not happen.
+                    // When this thread is interrupted by signal, mq_receive() will not return
+                    // partial read length and will return -1. And also no data is removed from mq.
+                    dlt_vlog(LOG_WARNING, "NWTSegmented: Could not read data fully from queue: %d\n", read);
                     continue;
                 }