Re: [PATCH rcu v2] 4/5] rcu-tasks: Move RCU Tasks self-tests to core_initcall()

[John Ogness]

On 2025-02-05, "Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote:
>> If there is no backlog, pr_flush() returns immediately.
>
> OK, so I don't need to add "if (IS_ENABLED(CONFIG_PREEMPT_RT))" to guard
> it, then?

For !CONFIG_PREEMPT_RT, if there are legacy consoles registered,
pr_flush() will additionally perform a blocking lock on the
console_lock. The kernel is in a clean shutdown path, so it should not
be a risk to block on the console_lock. But the console_lock is one of
the ugly global locks (semaphore, actually) we are working to remove
because sometimes it still causes problems.

@pmladek: What do you think? Should we have a CONFIG_PREEMPT_RT guard,
which would always be safe? Or do you feel comfortable performing a
console_lock() in the shutdown path for !CONFIG_PREEMPT_RT?

John