linux-kernel - Re: [patch V2 3/6] genirq: Add optional hardware synchronization for shutdown

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Message-ID: <alpine.DEB.2.21.1907012001550.1802@nanos.tec.linutronix.de>
Date:   Mon, 1 Jul 2019 20:02:07 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Marc Zyngier <marc.zyngier@....com>,
        Robert Hodaszi <Robert.Hodaszi@...i.com>
Subject: Re: [patch V2 3/6] genirq: Add optional hardware synchronization
 for shutdown

On Mon, 1 Jul 2019, Peter Zijlstra wrote:

> On Fri, Jun 28, 2019 at 01:11:51PM +0200, Thomas Gleixner wrote:
> > But that does not catch the case where the interrupt is on flight at the
> > hardware level but not yet serviced by the target CPU. That creates an
> > interesing race condition:
> 
> > + *	It does not check whether there is an interrupt on flight at the
> > + *	hardware level, but not serviced yet, as this might deadlock when
> > + *	called with interrupts disabled and the target CPU of the interrupt
> > + *	is the current CPU.
> 
> > +	/*
> > +	 * Make sure it's not being used on another CPU and if the chip
> > +	 * supports it also make sure that there is no (not yet serviced)
> > +	 * interrupt on flight at the hardware level.
> > +	 */
> > +	__synchronize_hardirq(desc, true);
> 
> s/on flight/in flight/ ?

yes