From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756035AbbKCUSb (ORCPT ); Tue, 3 Nov 2015 15:18:31 -0500 Received: from www.linutronix.de ([62.245.132.108]:46623 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755385AbbKCUSa (ORCPT ); Tue, 3 Nov 2015 15:18:30 -0500 Subject: Re: [v4.1.10-rt10][PATCH 1/2] genirq: introduce new generic_handle_irq_rt_wa() api To: Thomas Gleixner , Grygorii Strashko References: <1446492626-24396-1-git-send-email-grygorii.strashko@ti.com> <1446492626-24396-2-git-send-email-grygorii.strashko@ti.com> <563906C5.8030801@ti.com> Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, Sekhar Nori From: Sebastian Andrzej Siewior Message-ID: <56391694.3030105@linutronix.de> Date: Tue, 3 Nov 2015 21:18:28 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit 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 On 11/03/2015 08:51 PM, Thomas Gleixner wrote: >> where MAX_MSI_IRQS = 32 now, but potentially can be increased up to 256. > > And you really oversimplified the code above. The reality is: > > for (i = 0; i < MAX_MSI_CTRLS: i++) { > u32 status = read_msi_ctrl(i); > > for_each_bit(status) > handle_irq(); > } > > So sure, the worst case here is MAX_MSI_CTRLS * 32, but if all > possible 256 MSI interrupts are pending at the same time, you have > other problems than that. With threaded interrupts we would have 256 invocations of wake_up_process() so nothing should take ages. > Thanks, > > tglx Sebastian