tracing: Use trace_sched_process_free() instead of exit() for pid tracing

commit afcab636657421f7ebfa0783a91f90256bba0091 upstream.

On exit, if a process is preempted after the trace_sched_process_exit()
tracepoint but before the process is done exiting, then when it gets
scheduled in, the function tracers will not filter it properly against the
function tracing pid filters.

That is because the function tracing pid filters hooks to the
sched_process_exit() tracepoint to remove the exiting task's pid from the
filter list. Because the filtering happens at the sched_switch tracepoint,
when the exiting task schedules back in to finish up the exit, it will no
longer be in the function pid filtering tables.

This was noticeable in the notrace self tests on a preemptable kernel, as
the tests would fail as it exits and preempted after being taken off the
notrace filter table and on scheduling back in it would not be in the
notrace list, and then the ending of the exit function would trace. The test
detected this and would fail.

Cc: stable@vger.kernel.org
Cc: Namhyung Kim <namhyung@kernel.org>
Fixes: 1e10486ffee0a ("ftrace: Add 'function-fork' trace option")
Fixes: c37775d57830a ("tracing: Add infrastructure to allow set_event_pid to follow children"
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 9e831623d2deac7a9fe4f02d1ecc5c2ae49dc35f..7cbfccd2fb031ddbc3e71680e88160b3fa5f574f 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6242,12 +6242,12 @@ void ftrace_pid_follow_fork(struct trace_array *tr, bool enable)
        if (enable) {
                register_trace_sched_process_fork(ftrace_pid_follow_sched_process_fork,
                                                  tr);
-               register_trace_sched_process_exit(ftrace_pid_follow_sched_process_exit,
+               register_trace_sched_process_free(ftrace_pid_follow_sched_process_exit,
                                                  tr);
        } else {
                unregister_trace_sched_process_fork(ftrace_pid_follow_sched_process_fork,
                                                    tr);
-               unregister_trace_sched_process_exit(ftrace_pid_follow_sched_process_exit,
+               unregister_trace_sched_process_free(ftrace_pid_follow_sched_process_exit,
                                                    tr);
        }
 }

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 421166a39253aa7c23c53bb1fee60977db44fd6f..e72a44ecb81da0290ab3f6de3181c535e92a1da4 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -533,12 +533,12 @@ void trace_event_follow_fork(struct trace_array *tr, bool enable)
        if (enable) {
                register_trace_prio_sched_process_fork(event_filter_pid_sched_process_fork,
                                                       tr, INT_MIN);
-               register_trace_prio_sched_process_exit(event_filter_pid_sched_process_exit,
+               register_trace_prio_sched_process_free(event_filter_pid_sched_process_exit,
                                                       tr, INT_MAX);
        } else {
                unregister_trace_sched_process_fork(event_filter_pid_sched_process_fork,
                                                    tr);
-               unregister_trace_sched_process_exit(event_filter_pid_sched_process_exit,
+               unregister_trace_sched_process_free(event_filter_pid_sched_process_exit,
                                                    tr);
        }
 }