tracing: Place trace_pid_list logic into abstract functions

Instead of having the logic that does trace_pid_list open coded, wrap it in
abstract functions. This will allow a rewrite of the logic that implements
the trace_pid_list without affecting the users.

Note, this causes a change in behavior. Every time a pid is written into
the set_*_pid file, it creates a new list and uses RCU to update it. If
pid_max is lowered, but there was a pid currently in the list that was
higher than pid_max, those pids will now be removed on updating the list.
The old behavior kept that from happening.

The rewrite of the pid_list logic will no longer depend on pid_max,
and will return the old behavior.

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

1 files changed, 13 insertions, 0 deletions

diff --git a/kernel/trace/pid_list.h b/kernel/trace/pid_list.h
new file mode 100644
index 000000000000..80d0ecfe1536
--- /dev/null
+++ b/kernel/trace/pid_list.h
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* Do not include this file directly. */
+
+#ifndef _TRACE_INTERNAL_PID_LIST_H
+#define _TRACE_INTERNAL_PID_LIST_H
+
+struct trace_pid_list {
+	int			pid_max;
+	unsigned long		*pids;
+};
+
+#endif /* _TRACE_INTERNAL_PID_LIST_H */