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 da1710499698b0ed56ea89183d18befda56c0243..6c96b30f3d63b0a681de16deb50a6a96f6d0c61d 100644 (file)
--- 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);
        }