Re: [PATCH] locking: Revert switching guards to _irq_{disable,enable}()

[David Laight <david.laight.linux@gmail.com>]

On Thu, 27 Aug 2026 14:33:05 -0700
Boqun Feng <boqun@kernel.org> wrote:

....
> Yes, if we go to the level to unify all irq disabling with counter
> tracking then I think using arch_local_irq_disable() is possible and
> makes a lot of senses.

Where are you thinking of keeping the counter?
On non-x86 accessing it may be expensive.
The best bet is probably in 'current'.

Doesn't that make this valid?
	int c = current->irq_disable_count;
	if (c) {
		current->irq_disable_count = c + 1;
		return c;
	}
	disable_irq(); // asm("cli")
	interrupt_disable_barrier(); // ISTR arm needs this
	current->irq_disable_count = 1;
	return 0;
}

The task can be preempted in the middle - but that doesn't matter.

If spin_lock_irqsave() returns current->irq_disable_count then
any existing code that does lock chaining works unaltered.

David

> 
> Regards,
> Boqun
> 
> > Thanks,
> > 
> >         tglx
> >   
>