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From: Thomas Gleixner <tglx@kernel.org>
To: Dmitry Ilvokhin <d@ilvokhin.com>
Cc: LKML <linux-kernel@vger.kernel.org>, x86@kernel.org, Neil Horman
 <nhorman@tuxdriver.com>, Radu Rendec <radu@rendec.net>
Subject: Re: [patch v2 09/14] genirq: Expose irq_find_desc_at_or_after() in
 core code
In-Reply-To: <acWFdtV2FYHEwBZw@shell.ilvokhin.com>
References: <20260320131108.344376329@kernel.org>
 <20260320132102.638201987@kernel.org>
 <acWFdtV2FYHEwBZw@shell.ilvokhin.com>
Date: Thu, 26 Mar 2026 22:11:12 +0100
Message-ID: <87h5q2cn4f.ffs@tglx>
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On Thu, Mar 26 2026 at 19:13, Dmitry Ilvokhin wrote:
>> -static unsigned int irq_find_at_or_after(unsigned int offset)
>> +struct irq_desc *irq_find_desc_at_or_after(unsigned int offset)
>>  {
>>  	unsigned long index = offset;
>> -	struct irq_desc *desc;
>> -
>> -	guard(rcu)();
>
> Is the drop of guard(rcu)() intentional here? irq_get_next_irq()
> dereferences the returned pointer after mt_find() has dropped
> rcu_read_unlock(). Should it hold its own guard(rcu)() to keep the same
> behaviour as before?

Good catch. The caller of irq_find_at_or_after() needs to hold it.