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From: Thomas Gleixner <tglx@linutronix.de>
To: Paul Burton <paul.burton@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>,
	dianders@chromium.org, James Hogan <james.hogan@imgtec.com>,
	Brian Norris <briannorris@chromium.org>,
	Jason Cooper <jason@lakedaemon.net>,
	jeffy.chen@rock-chips.com, Marc Zyngier <marc.zyngier@arm.com>,
	linux-kernel@vger.kernel.org, linux-mips@linux-mips.org,
	tfiga@chromium.org
Subject: Re: [RFC PATCH v1 2/9] genirq: Support shared per_cpu_devid interrupts
Date: Tue, 26 Sep 2017 14:00:34 +0200 (CEST)
Message-ID: <alpine.DEB.2.20.1709261359330.1848@nanos> (raw)
In-Reply-To: <alpine.DEB.2.20.1709252259270.2418@nanos>

On Mon, 25 Sep 2017, Thomas Gleixner wrote:

> On Thu, 7 Sep 2017, Paul Burton wrote:
> > Up until now per_cpu_devid interrupts have not supported sharing. On
> > MIPS we have some percpu interrupts which are shared in many systems -
> > a single CPU interrupt line may be used to indicate a timer interrupt,
> > performance counter interrupt or fast debug channel interrupt. We have
> > up until now supported this with a series of hacks, wherein drivers call
> > each other's interrupt handlers & our MIPS GIC irqchip driver includes a
> > hack which configures the interrupt(s) for all CPUs. In order to allow
> > this mess to be cleaned up, this patch introduces support for shared
> > per_cpu_devid interrupts.
> > 
> > The major portion of this is supporting per_cpu_devid interrupts in
> > __handle_irq_event_percpu() and then making use of this, via
> > handle_irq_event_percpu(), from handler_percpu_devif_irq() to invoke the
> > handler for all actions associated with the shared interrupt. This does
> > have a few side effects worth noting:
> > 
> >  - per_cpu_devid interrupts will now add to the entropy pool via
> >    add_interrupt_randomness(), where they previously did not.
> > 
> >  - per_cpu_devid interrupts will record timings when IRQS_TIMINGS is
> >    set, via record_irq_time(), where they previously did not.
> > 
> >  - per_cpu_devid interrupts will handle an IRQ_WAKE_THREAD return from
> >    their handlers to wake a thread, where they previously did not.
> 
> That's broken because it lacks the magic synchronization which is described
> in the comment in __irq_wake_thread().

Aside of that to make that work at all would require per cpu threads and
not a single systemwide thread.

Thanks,

	tglx

  reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1682867.tATABVWsV9@np-p-burton>
2017-09-07 23:25 ` [RFC PATCH v1 0/9] Support shared percpu interrupts; clean up MIPS hacks Paul Burton
2017-09-07 23:25   ` [RFC PATCH v1 1/9] genirq: Allow shared interrupt users to opt into IRQ_NOAUTOEN Paul Burton
2017-09-07 23:25   ` [RFC PATCH v1 2/9] genirq: Support shared per_cpu_devid interrupts Paul Burton
2017-09-25 21:06     ` Thomas Gleixner
2017-09-26 12:00       ` Thomas Gleixner [this message]
2017-10-19 14:08         ` Thomas Gleixner
2017-09-07 23:25   ` [RFC PATCH v1 3/9] genirq: Introduce irq_is_percpu_devid() Paul Burton
2017-09-07 23:25   ` [RFC PATCH v1 4/9] MIPS: Remove perf_irq interrupt sharing fallback Paul Burton
2017-09-07 23:25   ` [RFC PATCH v1 5/9] MIPS: Remove perf_irq Paul Burton
2017-09-07 23:25   ` [RFC PATCH v1 6/9] MIPS: perf: percpu_devid interrupt support Paul Burton
2017-10-19 14:12     ` Thomas Gleixner
2017-09-07 23:25   ` [RFC PATCH v1 7/9] MIPS: cevt-r4k: " Paul Burton
2017-09-07 23:25   ` [RFC PATCH v1 8/9] irqchip: mips-cpu: Set timer, FDC & perf interrupts percpu_devid Paul Burton
2017-09-07 23:25   ` [RFC PATCH v1 9/9] irqchip: mips-gic: Remove gic_all_vpes_local_irq_controller Paul Burton

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