On Wed, 28 Feb 2024 11:38:29 -0800 "Paul E. McKenney" <[email protected]> wrote:
> 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. > > Only build tested. > > Signed-off-by: Paul E. McKenney <[email protected]> > Cc: Steven Rostedt <[email protected]> > Cc: Masami Hiramatsu <[email protected]> > Cc: Mark Rutland <[email protected]> > Cc: Mathieu Desnoyers <[email protected]> > Cc: Ankur Arora <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: <[email protected]> > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index 2da4eaa2777d6..c9e6c69cf3446 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -3156,7 +3156,7 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command) > * synchronize_rcu_tasks() will wait for those tasks to > * execute and either schedule voluntarily or enter user space. > */ > - if (IS_ENABLED(CONFIG_PREEMPTION)) > + if (IS_ENABLED(CONFIG_TASKS_RCU)) > synchronize_rcu_tasks(); What happens if CONFIG_TASKS_RCU is not enabled? Does synchronize_rcu_tasks() do anything? Or is it just a synchronize_rcu()? If that's the case, perhaps just remove the if statement and make it: synchronize_rcu_tasks(); Not sure an extra synchronize_rcu() will hurt (especially after doing a synchronize_rcu_tasks_rude() just before hand! -- Steve
