linux-kernel - Re: [GIT pull] irq updates for 4.13

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Message-ID: <alpine.DEB.2.20.1707111815280.1799@nanos>
Date:   Tue, 11 Jul 2017 18:19:55 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
cc:     Tony Lindgren <tony@...mide.com>,
        Sebastian Reichel <sebastian.reichel@...labora.co.uk>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Pavel Machek <pavel@....cz>,
        Linus Walleij <linus.walleij@...aro.org>,
        Grygorii Strashko <grygorii.strashko@...com>
Subject: Re: [GIT pull] irq updates for 4.13

On Tue, 11 Jul 2017, Linus Torvalds wrote:

> On Tue, Jul 11, 2017 at 7:41 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> >
> > Ah. Now that makes sense.
> >
> > Unpatched the ordering is:
> >
> >           chip_bus_lock(desc);
> >           irq_request_resources(desc);
> 
> I *looked* at that ordering and then went "Naah, that makes no sense".
> 
> But if that's the only issue, how about we just re-order those things
> - we still don't need to move the irq_request_resources() into the
> spinlock, we just move it to below the chip_bus_lock().
> 
> IOW, something like the (COMPLETELY UNTEESTED!) attached patch.
> 
> This assumes that the chip_bus_lock() thing is still ok for the RT
> case, but it looks like it might be: the only other one I looked at
> (apart from the gpio-omap one) used a mutex.

I looked through all of them and the only special case is gpio-omap.

What I do not understand here is that we have already power management
around all of that.

       irq_chip_pm_get(&desc->irq_data);
       ...
       chip_bus_lock(desc);
       ...
       chip_bus_unlock_sync(desc);
       ...
       irq_chip_pm_put(&desc->irq_data);

So why is that not sufficient and needs extra magic in that GPIO driver?

Thanks,

	tglx