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From: Thomas Gleixner <tglx@kernel.org>
To: Boqun Feng <boqun@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org,
 linux-tip-commits@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH] locking: Revert switching guards to
 _irq_{disable,enable}()
In-Reply-To: <apNtQWqOgwF5_Ctq@tardis.local>
References: <877bldhkmq.ffs@fw13> <ao4lO7U7L-7Zice1@tardis.local>
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 <87jypbfu1t.ffs@fw13> <apBrZuxU8bmCgG8h@tardis.local>
 <87bjanfmzz.ffs@fw13> <apCS3T63WUxHd1GH@tardis.local>
 <87wltbdvmd.ffs@fw13> <87mru5et6r.ffs@fw13>
 <apNtQWqOgwF5_Ctq@tardis.local>
Date: Sun, 30 Aug 2026 22:01:12 +0200
Message-ID: <87se3vcr93.ffs@fw13>
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On Sat, Aug 29 2026 at 16:37, Boqun Feng wrote:
> On Sat, Aug 29, 2026 at 01:11:56AM +0200, Thomas Gleixner wrote:
>> +static __always_inline void __raw_local_irq_restore(unsigned long cnt)
>> +{
>> +	debug_assert((preempt_count() & HARDIRQ_DISABLE_MASK) == (cnt + HARDIRQ_DISABLE_OFFSET));
>> +
>> +	if (!(__preempt_count_sub_return(HARDIRQ_DISABLE_OFFSET) & HARDIRQ_DISABLE_MASK))
>> +		arch_local_irq_enable();
>> +}
>
> And while we are at, we can just introduce a
> raw_local_irq_restore_auto() (definitely needs a better name), which
> doesn't need a cnt:
>
> static __always_inline void __raw_local_irq_restore_auto(void)
> {
> 	debug_assert((preempt_count() & HARDIRQ_DISABLE_MASK));
>
> 	if (!(__preempt_count_sub_return(HARDIRQ_DISABLE_OFFSET) & HARDIRQ_DISABLE_MASK))
> 		arch_local_irq_enable();
> }

Yes, we can add something like this once we got the design and the debug
infrastructure in place. For now the count is helpful to debug stuff and
we want to have something equivalent at least for lockdep builds.

Thanks,

        tglx