This is a note to let you know that I've just added the patch titled
tracing: Use trace_sched_process_free() instead of exit() for pid tracing
to the 5.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-use-trace_sched_process_free-instead-of-exit-for-pid-tracing.patch
and it can be found in the queue-5.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From afcab636657421f7ebfa0783a91f90256bba0091 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
Date: Tue, 4 Aug 2020 20:00:02 -0400
Subject: tracing: Use trace_sched_process_free() instead of exit() for pid tracing
From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
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@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/ftrace.c | 4 ++--
kernel/trace/trace_events.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6969,12 +6969,12 @@ void ftrace_pid_follow_fork(struct trace
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);
}
}
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -538,12 +538,12 @@ void trace_event_follow_fork(struct trac
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);
}
}
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-5.8/tracing-use-trace_sched_process_free-instead-of-exit-for-pid-tracing.patch
queue-5.8/tracing-hwlat-honor-the-tracing_cpumask.patch
queue-5.8/kprobes-fix-null-pointer-dereference-at-kprobe_ftrace_handler.patch
queue-5.8/ftrace-setup-correct-ftrace_fl_regs-flags-for-module.patch
