linux-kernel - Re: [RFC PATCH v2 3/4] irq: Introduce IRQ_HANDLED

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Date: Wed, 21 Feb 2024 18:04:21 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Leonardo Bras <leobras@...hat.com>
Cc: Leonardo Bras <leobras@...hat.com>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>, Tony
 Lindgren <tony@...mide.com>, Andy Shevchenko
 <andriy.shevchenko@...ux.intel.com>, John Ogness
 <john.ogness@...utronix.de>, Ilpo Järvinen
 <ilpo.jarvinen@...ux.intel.com>, Uwe Kleine-König
 <u.kleine-koenig@...gutronix.de>, Florian Fainelli
 <florian.fainelli@...adcom.com>, Shanker Donthineni
 <sdonthineni@...dia.com>, linux-kernel@...r.kernel.org,
 linux-serial@...r.kernel.org
Subject: Re: [RFC PATCH v2 3/4] irq: Introduce IRQ_HANDLED_MANY

On Wed, Feb 21 2024 at 16:41, Thomas Gleixner wrote:
> On Wed, Feb 21 2024 at 02:39, Leonardo Bras wrote:
> But as I pointed out above the detection logic is flawed due to the
> unconditional accumulation. Can you give the uncompiled below a test
> ride with your scenario?

Bah. Ignore this. I misread the code completely. No idea where my brain
was.

This thing triggers only when there are 100K interrupts and 99.9k of
them unhandled. The 100k total resets the unhandled counts.

Though one thing which strikes me odd is that this actually triggers at
all because it needs 99.9k unhandled out of 100k total. That means on
average every thread handler invocation handles 1000 hardware interrupts
in one go. Is that even realistic?

Thanks,

        tglx