Re: [PATCH v4 05/17] irq & spin_lock: Add counted interrupt disabling/enabling

[Boqun Feng <boqun@kernel.org>]

On Wed, Aug 05, 2026 at 07:40:18PM +0530, Shrikanth Hegde wrote:
> 
> Hi Boqun,
> 
> > 
> > Something as below? Going to send it to kernel build bot and see if it
> > works for all configs.
> > 
> > ----------------->8
> > diff --git a/include/linux/interrupt_rc.h b/include/linux/interrupt_rc.h
> > index b9a7f05ecf42..39f30bc65548 100644
> > --- a/include/linux/interrupt_rc.h
> > +++ b/include/linux/interrupt_rc.h
> > @@ -12,6 +12,7 @@
> >    */
> > 
> >   #include <linux/irqflags.h>
> > +#include <linux/debug_locks.h>
> >   #include <linux/preempt.h>
> >   #include <linux/processor.h>
> >   #include <linux/smp.h>
> > @@ -63,6 +64,12 @@ static inline void local_interrupt_disable(void)
> > 
> >          new_count = hardirq_disable_enter();
> > 
> > +       /* Is hardirq disable count overflow soon? */
> > +       if (IS_ENABLED(CONFIG_DEBUG_PREEMPT))
> > +               DEBUG_LOCKS_WARN_ON((new_count & HARDIRQ_DISABLE_MASK) +
> > +                                   (10 << HARDIRQ_DISABLE_SHIFT) >
> > +                                   HARDIRQ_DISABLE_MASK);
> > +
> 
> This needs a return here right? Else we will see warning for 10 times
> and then overflow happens and we will call _local_interrupt_disable. No?
> 

DEBUG_LOCKS_WARN_ON() uses debug_locks_off() to avoid this, so we won't
see it 10 times. The reason not using return here, because we would
introduce unpaired local_interrupt_disable() if we returned:

	// hardirq disable count is n
	local_interrupt_disable(); // hardirq disable count is n + 1

	local_interrupt_disable(); <- trigger the warning, if we return
				   // hardirq disable count is n + 1

	local_interrupt_enable(); // hardirq disable count is n

	local_interrupt_enable(); // hardirq disable count is n - 1

Regards,
Boqun

> Not sure, if below is any better? (Igore whitespace mangling)
> 
> if (IS_ENABLED(CONFIG_DEBUG_PREEMPT) &&
>     DEBUG_LOCKS_WARN_ON((preempt_count() & HARDIRQ_DISABLE_MASK) >=
> 			 HARDIRQ_DISABLE_MASK - (10 << HARDIRQ_DISABLE_SHIFT)))
> 	return;
> 
> >          /* Interrupts can happen here, but it's OK, see __irq_exit_rcu(). */
> > 
> >          if ((new_count & HARDIRQ_DISABLE_MASK) == HARDIRQ_DISABLE_OFFSET)
> > @@ -73,6 +80,11 @@ static inline void local_interrupt_enable(void)
> >   {
> >          int new_count;
> > 
> > +       /* Unpaired local_interrupt_enable()? Warn and abort. */
> > +       if (IS_ENABLED(CONFIG_DEBUG_PREEMPT) &&
> > +           DEBUG_LOCKS_WARN_ON((preempt_count() & HARDIRQ_DISABLE_MASK) == 0))
> > +               return;
> > +
> >          new_count = hardirq_disable_exit();
> > 
> >          if ((new_count & HARDIRQ_DISABLE_MASK) == 0) >
>