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Date: Sat, 24 Jun 2017 11:21:43 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
cc: Brian Norris <briannorris@chromium.org>,
        Heiko Stuebner <heiko@sntech.de>,
        Linus Walleij <linus.walleij@linaro.org>,
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        Doug Anderson <dianders@chromium.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Tony Lindgren <tony@atomide.com>
Subject: Re: [PATCH for 4.12] Revert "pinctrl: rockchip: avoid hardirq-unsafe
 functions in irq_chip"
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References: <20170517225634.GA11404@google.com> <20170527021900.GA119873@google.com> <20170623205911.GA143883@google.com> <alpine.DEB.2.20.1706232353220.2234@nanos> <20170623224049.GP3721@linux.vnet.ibm.com>
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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