Document filter usage

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/doc/man/lttng.1 b/doc/man/lttng.1
index 6bbf3154e3dd81151802bd63f51112f7df70f96a..417f799c49c25a48275d35ba0c5e7e67315af96d 100644 (file)
--- a/doc/man/lttng.1
+++ b/doc/man/lttng.1
@@ -340,6 +340,13 @@ file.
         Enabling syscalls tracing (kernel tracer), you will not be able to disable them
         with disable-event. This is a known limitation. You can disable the entire
         channel to do the trick.
+\-\-filter 'expression'
+       Set a filter on a newly enabled event.
+        Filter expression on event fields event recording
+        depends on evaluation. Only specify on first activation
+        of a given event within a session. Filter only allowed
+        when enabling events within a session before tracing is
+        started.
 .fi
 
 .IP "\fBdisable-channel\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"

diff --git a/src/bin/lttng/commands/enable_events.c b/src/bin/lttng/commands/enable_events.c
index 3f304a0902ad398bfddacc76ba97ca6595836685..de1796ad8ed0e7fa8f6fe06d363c7ad33787e8f0 100644 (file)
--- a/src/bin/lttng/commands/enable_events.c
+++ b/src/bin/lttng/commands/enable_events.c
@@ -168,6 +168,11 @@ static void usage(FILE *ofp)
        fprintf(ofp, "    --filter \'expression\'\n");
        fprintf(ofp, "                           Filter expression on event fields,\n");
        fprintf(ofp, "                           event recording depends on evaluation.\n");
+       fprintf(ofp, "                           Only specify on first activation of\n");
+       fprintf(ofp, "                           a given event within a session.\n");
+       fprintf(ofp, "                           Filter only allowed when enabling\n");
+       fprintf(ofp, "                           events within a session before tracing\n");
+       fprintf(ofp, "                           is started.\n");
        fprintf(ofp, "\n");
 }