linux-kernel - Re: [PATCH] x86/ioapic: add IO-APIC irq

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Date:   Wed, 18 Jan 2017 11:46:46 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Ruslan Ruslichenko <rruslich@...co.com>
cc:     Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        xe-linux-external@...co.com
Subject: Re: [PATCH] x86/ioapic: add IO-APIC irq_chip retrigger hook

On Tue, 17 Jan 2017, Ruslan Ruslichenko wrote:

> After commit d32932d02e18  ("x86/irq: Convert IOAPIC to use hierarchical
> irqdomain interfaces") IO-APIC is switched to hierarchical irqdomain
> implementation. Also this patch removed irq_retrigger hook for IO-APIC
> chip which seem to be wrong. Without this hook some edge-triggered irq's
> might be lost, since kernel uses it to retrigger edge irq's triggered
> while they are being handled or disabled by driver

Restoring the callbacks is the right thing to do, but there is no problem
because if the retrigger callback is empty then pending edge interrupts are
resent by software. It's just less efficient, but not a issue.

Thanks,

	tglx