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Date: Mon, 8 Sep 2014 17:23:16 +0100 From: Russell King - ARM Linux <linux@....linux.org.uk> To: Daniel Thompson <daniel.thompson@...aro.org> Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, patches@...aro.org, linaro-kernel@...ts.linaro.org, John Stultz <john.stultz@...aro.org>, Thomas Gleixner <tglx@...utronix.de>, Sumit Semwal <sumit.semwal@...aro.org>, Jason Cooper <jason@...edaemon.net> Subject: Re: [PATCH v3 5/5] irqchip: gic: Add support for IPI FIQ On Mon, Sep 08, 2014 at 04:28:35PM +0100, Daniel Thompson wrote: > @@ -604,8 +731,19 @@ static void gic_raise_softirq(const struct cpumask *mask, unsigned int irq) > { > int cpu; > unsigned long flags, map = 0; > + unsigned long softint; > > - raw_spin_lock_irqsave(&irq_controller_lock, flags); > + /* > + * The locking in this function ensures we don't use stale cpu mappings > + * and thus we never route an IPI to the wrong physical core during a > + * big.LITTLE switch. The switch code takes both of these locks meaning > + * we can choose whichever lock is safe to use from our current calling > + * context. > + */ > + if (in_nmi()) > + raw_spin_lock(&fiq_safe_migration_lock); > + else > + raw_spin_lock_irqsave(&irq_controller_lock, flags); Firstly, why would gic_raise_softirq() be called in FIQ context? Secondly, this doesn't save you. If you were in the middle of gic_migrate_target() when the FIQ happened that (for some reason prompted you to call this), you would immediately deadlock trying to that this IRQ. I suggest not even trying to solve this "race" which I don't think is one which needs to even be considered (due to the first point.) -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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