Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030528AbdIZMBE (ORCPT ); Tue, 26 Sep 2017 08:01:04 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:48345 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965399AbdIZMAu (ORCPT ); Tue, 26 Sep 2017 08:00:50 -0400 Date: Tue, 26 Sep 2017 14:00:34 +0200 (CEST) From: Thomas Gleixner To: Paul Burton cc: Ralf Baechle , dianders@chromium.org, James Hogan , Brian Norris , Jason Cooper , jeffy.chen@rock-chips.com, Marc Zyngier , 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 In-Reply-To: Message-ID: References: <1682867.tATABVWsV9@np-p-burton> <20170907232542.20589-1-paul.burton@imgtec.com> <20170907232542.20589-3-paul.burton@imgtec.com> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1732 Lines: 37 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