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

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Message-ID: <20190701145628.GC3402@hirez.programming.kicks-ass.net>
Date:   Mon, 1 Jul 2019 16:56:28 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
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 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/ ?