Re: [patch V4 part 1 24/36] lockdep: Prepare for noinstr sections

Steven Rostedt
2020-05-08T00:24:06Z

On Tue, 05 May 2020 15:16:26 +0200
Thomas Gleixner <tglx@linutronix.de> wrote:
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -3639,9 +3639,6 @@ static void __trace_hardirqs_on_caller(u
> {
> struct task_struct *curr = current;
>
> - /* we'll do an OFF -> ON transition: */
> - curr->hardirqs_enabled = 1;
> -
> /*
> * We are going to turn hardirqs on, so set the
> * usage bit for all held locks:
> @@ -3653,16 +3650,13 @@ static void __trace_hardirqs_on_caller(u
> * bit for all held locks. (disabled hardirqs prevented
> * this bit from being set before)
> */
> - if (curr->softirqs_enabled)
> + if (curr->softirqs_enabled) {
> if (!mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ))
> return;

The above can be turned into:

if (curr->softirqs_enabled)
mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);

No need for the condition or the return.

> -
> - curr->hardirq_enable_ip = ip;
> - curr->hardirq_enable_event = ++curr->irq_events;
> - debug_atomic_inc(hardirqs_on_events);
> + }
> }
>
> -void lockdep_hardirqs_on(unsigned long ip)
> +void lockdep_hardirqs_on_prepare(unsigned long ip)
> {
> if (unlikely(!debug_locks || current->lockdep_recursion))
> return;
> @@ -3698,20 +3692,62 @@ void lockdep_hardirqs_on(unsigned long i
> if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
> return;
>
> + current->hardirq_chain_key = current->curr_chain_key;
> +
> current->lockdep_recursion++;
> __trace_hardirqs_on_caller(ip);
> lockdep_recursion_finish();
> }
> -NOKPROBE_SYMBOL(lockdep_hardirqs_on);
> +EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
> +
> +void noinstr lockdep_hardirqs_on(unsigned long ip)
> +{

Would be nice to have some kerneldoc explaining the difference between
lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().

-- Steve