tracing: Create set_event_notrace_pid to not trace tasks

There's currently a way to select a task that should only have its events
traced, but there's no way to select a task not to have itsevents traced.
Add a set_event_notrace_pid file that acts the same as set_event_pid (and is
also affected by event-fork), but the task pids in this file will not be
traced even if they are listed in the set_event_pid file. This makes it easy
for tools like trace-cmd to "hide" itself from beint traced by events when
it is recording other tasks.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 2 insertions, 9 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7239d9acd09f..0bb62e64280c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6987,11 +6987,6 @@ void ftrace_pid_follow_fork(struct trace_array *tr, bool enable)
 	}
 }
 
-enum {
-	TRACE_PIDS		= BIT(0),
-	TRACE_NO_PIDS		= BIT(1),
-};
-
 static void clear_ftrace_pids(struct trace_array *tr, int type)
 {
 	struct trace_pid_list *pid_list;
@@ -7004,13 +6999,11 @@ static void clear_ftrace_pids(struct trace_array *tr, int type)
 						lockdep_is_held(&ftrace_lock));
 
 	/* Make sure there's something to do */
-	if (!(((type & TRACE_PIDS) && pid_list) ||
-	      ((type & TRACE_NO_PIDS) && no_pid_list)))
+	if (!pid_type_enabled(type, pid_list, no_pid_list))
 		return;
 
 	/* See if the pids still need to be checked after this */
-	if (!((!(type & TRACE_PIDS) && pid_list) ||
-	      (!(type & TRACE_NO_PIDS) && no_pid_list))) {
+	if (!still_need_pid_events(type, pid_list, no_pid_list)) {
 		unregister_trace_sched_switch(ftrace_filter_pid_sched_switch_probe, tr);
 		for_each_possible_cpu(cpu)
 			per_cpu_ptr(tr->array_buffer.data, cpu)->ftrace_ignore_pid = FTRACE_PID_TRACE;