linux-kernel - Re: [PATCH for 4.12] Revert "pinctrl: rockchip: avoid hardirq-unsafe functions in irq

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Date:   Sat, 24 Jun 2017 11:21:43 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
cc:     Brian Norris <briannorris@...omium.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-rockchip@...ts.infradead.org,
        Julia Cartwright <julia@...com>,
        LKML <linux-kernel@...r.kernel.org>, linux-gpio@...r.kernel.org,
        John Keeping <john@...anate.com>, linux-pm@...r.kernel.org,
        Doug Anderson <dianders@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH for 4.12] Revert "pinctrl: rockchip: avoid hardirq-unsafe
 functions in irq_chip"

On Fri, 23 Jun 2017, Paul E. McKenney wrote:
> On Sat, Jun 24, 2017 at 12:12:49AM +0200, Thomas Gleixner wrote:
> > which added that RCU locking stuff and thereby broke the long existing
> > bus_lock() facility of the interrupt core.
> > 
> > irq_bus_lock/unlock was explicitely made to allow sleeping locks for
> > interrupt chips which hang behind slow busses like i2c or spi. It took us
> > quite some effort to get this done and that patch broke it permanently.
> > 
> > I'm not sure what to do here. This is an ever recurring issue simply
> > because RT requires that sleeping locks can be taken inside rcu locked
> > regions. So sooner than later we need a resoilution for that problem.
> 
> The usual advice would be for 4990d4fe327b ("PM / Wakeirq: Add automated
> device wake IRQ handling") to use SRCU rather than RCU.  Is there some
> reason that won't work?

I can't see one. So yes, we should rather convert that stuff to SRCU
instead of playing ping pong forever.

Thanks,

	tglx