The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0878355b51f5f26632e652c848a8e174bb02d22d Mon Sep 17 00:00:00 2001 From: Nikita Yushchenko nikita.yushchenko@virtuozzo.com Date: Sun, 9 Jan 2022 18:34:59 +0300 Subject: [PATCH] tracing/osnoise: Properly unhook events if start_per_cpu_kthreads() fails

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@virtuoz...

Cc: stable@vger.kernel.org Fixes: bce29ac9ce0b ("trace: Add osnoise tracer") Acked-by: Daniel Bristot de Oliveira bristot@kernel.org Signed-off-by: Nikita Yushchenko nikita.yushchenko@virtuozzo.com Signed-off-by: Steven Rostedt rostedt@goodmis.org

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c index 4719a848bf17..36d9d5be08b4 100644 --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -2122,6 +2122,13 @@ static int osnoise_hook_events(void) 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 */ @@ -2154,7 +2161,14 @@ 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; }

@@ -2185,9 +2199,7 @@ 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)