This is a note to let you know that I've just added the patch titled
tracing/osnoise: Properly unhook events if start_per_cpu_kthreads() fails
to the 5.16-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-osnoise-properly-unhook-events-if-start_per_cpu_kthreads-fails.patch
and it can be found in the queue-5.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0878355b51f5f26632e652c848a8e174bb02d22d Mon Sep 17 00:00:00 2001
From: Nikita Yushchenko <nikita.yushchenko@xxxxxxxxxxxxx>
Date: Sun, 9 Jan 2022 18:34:59 +0300
Subject: tracing/osnoise: Properly unhook events if start_per_cpu_kthreads() fails
From: Nikita Yushchenko <nikita.yushchenko@xxxxxxxxxxxxx>
commit 0878355b51f5f26632e652c848a8e174bb02d22d upstream.
If start_per_cpu_kthreads() called from osnoise_workload_start() returns
error, event hooks are left in broken state: unhook_irq_events() called
but unhook_thread_events() and unhook_softirq_events() not called, and
trace_osnoise_callback_enabled flag not cleared.
On the next tracer enable, hooks get not installed due to
trace_osnoise_callback_enabled flag.
And on the further tracer disable an attempt to remove non-installed
hooks happened, hitting a WARN_ON_ONCE() in tracepoint_remove_func().
Fix the error path by adding the missing part of cleanup.
While at this, introduce osnoise_unhook_events() to avoid code
duplication between this error path and normal tracer disable.
Link: https://lkml.kernel.org/r/20220109153459.3701773-1-nikita.yushchenko@xxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Fixes: bce29ac9ce0b ("trace: Add osnoise tracer")
Acked-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Signed-off-by: Nikita Yushchenko <nikita.yushchenko@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace_osnoise.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -2123,6 +2123,13 @@ out_unhook_irq:
return -EINVAL;
}
+static void osnoise_unhook_events(void)
+{
+ unhook_thread_events();
+ unhook_softirq_events();
+ unhook_irq_events();
+}
+
/*
* osnoise_workload_start - start the workload and hook to events
*/
@@ -2155,7 +2162,14 @@ static int osnoise_workload_start(void)
retval = start_per_cpu_kthreads();
if (retval) {
- unhook_irq_events();
+ trace_osnoise_callback_enabled = false;
+ /*
+ * Make sure that ftrace_nmi_enter/exit() see
+ * trace_osnoise_callback_enabled as false before continuing.
+ */
+ barrier();
+
+ osnoise_unhook_events();
return retval;
}
@@ -2186,9 +2200,7 @@ static void osnoise_workload_stop(void)
stop_per_cpu_kthreads();
- unhook_irq_events();
- unhook_softirq_events();
- unhook_thread_events();
+ osnoise_unhook_events();
}
static void osnoise_tracer_start(struct trace_array *tr)
Patches currently in stable-queue which might be from nikita.yushchenko@xxxxxxxxxxxxx are
queue-5.16/tracing-osnoise-properly-unhook-events-if-start_per_cpu_kthreads-fails.patch
