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Subject: Re: [patch 3/8] x86/apic: Provide apic_ack_irq()
To: Thomas Gleixner <tglx@linutronix.de>
CC: LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Borislav Petkov <bp@alien8.de>,
        Dmitry Safonov <0x7f454c46@gmail.com>,
        Tariq Toukan <tariqt@mellanox.com>,
        Song Liu <liu.song.a23@gmail.com>,
        Joerg Roedel <jroedel@suse.de>,
        Mike Travis <mike.travis@hpe.com>, <stable@vger.kernel.org>
References: <20180604162224.471925894@linutronix.de>
 <94117bd8-352b-1077-e8ae-8722d7ec213f@cn.fujitsu.com>
 <alpine.DEB.2.21.1806051339020.1591@nanos.tec.linutronix.de>
From: Dou Liyang <douly.fnst@cn.fujitsu.com>
Message-ID: <de96585f-9b8d-4536-a9d5-32a718e3eb4d@cn.fujitsu.com>
Date: Wed, 6 Jun 2018 11:48:55 +0800
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Hi Thomas,

At 06/05/2018 07:41 PM, Thomas Gleixner wrote:
> On Tue, 5 Jun 2018, Dou Liyang wrote:
>>> +{
>>> +	if (unlikely(irqd_is_setaffinity_pending(irqd)))
>>
>> Affinity pending is also judged in
>>
>>> +		irq_move_irq(irqd);
>>
>> If we can remove the if(...) statement here
> 
> That requires to fix all call sites in ia64 and that's why I didn't.  But

I didn't express clearly, I meant remove the if(...) statement from
apic_ack_irq(), it doesn't require to fix the call sites in ia64.

+void apic_ack_irq(struct irq_data *irqd)
+{
+	irq_move_irq(irqd);
+	ack_APIC_irq();
+}

BTW, If apic_ack_irq() can accept _any_ irq_data when hierarchical
irqdomains are enabled[1]? If it is true, If there is a situation in
the original code that we should avoid:

   If the top-level irq_data has the IRQD_SETAFFINITY_PENDING state, but
   non-top-level irq_data state not, when using non-top-level irq_data in
   apic_ack_irq(), we may skip the irq_move_irq() which we should call.

[1] commit 77ed42f18edd("genirq: Prevent crash in irq_move_irq()")

> we can make irq_move_irq() an inline function and have the check in the
> inline.
> 

I don't know why do we need to make irq_move_irq() an inline function.

And, yes, irq_move_irq() has already had the check

         ...
   	if (likely(!irqd_is_setaffinity_pending(idata)))
		return;
         ...

Thanks,
	dou