FAILED: patch "[PATCH] tracing/osnoise: Properly unhook events if" failed to apply to 5.15-stable tree

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 <[email protected]>.

thanks,

greg k-h

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

From 0878355b51f5f26632e652c848a8e174bb02d22d Mon Sep 17 00:00:00 2001
From: Nikita Yushchenko <[email protected]>
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.

index 4719a848bf17..36d9d5be08b4 100644
@@ -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)

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.

---
 kernel/trace/trace_osnoise.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

index c4f14fb98aaa..65a518649997 100644
@@ -1932,6 +1932,13 @@ static int osnoise_hook_events(void)
 	return -EINVAL;
 }
 
+static void osnoise_unhook_events(void)
+{
+	unhook_thread_events();
+	unhook_softirq_events();
+	unhook_irq_events();
+}
+
 static int __osnoise_tracer_start(struct trace_array *tr)
 {
 	int retval;

@@ -1949,7 +1956,14 @@ static int __osnoise_tracer_start(struct trace_array *tr)
 
 	retval = start_per_cpu_kthreads(tr);
 	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;
 	}
 

@@ -1981,9 +1995,7 @@ static void osnoise_tracer_stop(struct trace_array *tr)
 
 	stop_per_cpu_kthreads();
 
-	unhook_irq_events();
-	unhook_softirq_events();
-	unhook_thread_events();
+	osnoise_unhook_events();
 
 	osnoise_busy = false;
 }

2.30.2

Now queued up, thanks.

greg k-h