From: Paul E. McKenney <paulmck@kernel.org>
Date: Wed, 28 Feb 2024 19:30:43 +0000 (-0800)
Subject: ftrace: Choose RCU Tasks based on TASKS_RCU rather than PREEMPTION
X-Git-Tag: v6.10-rc1~234^2^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=64ec8b6ad61997262fb3373970377f5fb709454b;p=thirdparty%2Fkernel%2Flinux.git

ftrace: Choose RCU Tasks based on TASKS_RCU rather than PREEMPTION

The advent of CONFIG_PREEMPT_AUTO, AKA lazy preemption, will mean that
even kernels built with CONFIG_PREEMPT_NONE or CONFIG_PREEMPT_VOLUNTARY
might see the occasional preemption, and that this preemption just might
happen within a trampoline.

Therefore, update ftrace_shutdown() to invoke synchronize_rcu_tasks()
based on CONFIG_TASKS_RCU instead of CONFIG_PREEMPTION.

[ paulmck: Apply Steven Rostedt feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Ankur Arora <ankur.a.arora@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <linux-trace-kernel@vger.kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index da1710499698b..6c96b30f3d63b 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3157,8 +3157,7 @@ out:
 		 * synchronize_rcu_tasks() will wait for those tasks to
 		 * execute and either schedule voluntarily or enter user space.
 		 */
-		if (IS_ENABLED(CONFIG_PREEMPTION))
-			synchronize_rcu_tasks();
+		synchronize_rcu_tasks();
 
 		ftrace_trampoline_free(ops);
 	}