tracing: Call on_each_cpu() when adding or removing single pids from set_event_pid

For the case where pids are already in set_event_pid, and one is added or
removed then each CPU should be checked to make sure that the new or old pid
is on or not on a CPU.

 For example:

 # echo 123 >> set_event_pid

or

 # echo '!123' >> set_event_pid

Link: http://lkml.kernel.org/r/20151030061643.GA19480@cac
Suggested-by: Jiaxing Wang <hello.wjx@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index fb0261e..292bccf 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1729,14 +1729,15 @@ ftrace_event_pid_write(struct file *filp, const char __user *ubuf,
                                                 tr, INT_MAX);
                register_trace_prio_sched_wakeup(event_filter_pid_sched_wakeup_probe_post,
                                                 tr, 0);
-
-               /*
-                * Ignoring of pids is done at task switch. But we have to
-                * check for those tasks that are currently running.
-                */
-               on_each_cpu(ignore_task_cpu, tr, 1);
        }
 
+       /*
+        * Ignoring of pids is done at task switch. But we have to
+        * check for those tasks that are currently running.
+        * Always do this in case a pid was appended or removed.
+        */
+       on_each_cpu(ignore_task_cpu, tr, 1);
+
        mutex_unlock(&event_mutex);
 
        ret = read;