From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752152AbbBVWai (ORCPT ); Sun, 22 Feb 2015 17:30:38 -0500 Received: from gate.crashing.org ([63.228.1.57]:59970 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752021AbbBVWah (ORCPT ); Sun, 22 Feb 2015 17:30:37 -0500 Message-ID: <1424644212.4980.14.camel@kernel.crashing.org> Subject: Re: [PATCH] powerpc: re-enable dynticks From: Benjamin Herrenschmidt To: Frederic Weisbecker Cc: Michael Ellerman , Paul Clarke , "linuxppc-dev@lists.ozlabs.org" , LKML Date: Mon, 23 Feb 2015 09:30:12 +1100 In-Reply-To: References: <54DE52BC.3020303@us.ibm.com> <1424045319.3018.2.camel@ellerman.id.au> <1424059606.21410.41.camel@kernel.crashing.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.7-0ubuntu1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2015-02-22 at 23:13 +0100, Frederic Weisbecker wrote: > Yes that should work. After all "self-IPI" is an oxymoron. One would > expect an IPI to be triggered by an irq controller but if such > operation isn't supported with the current CPU being both source and > destination, anything triggering the desired callback in an interrupt > context in a reasonable amount of time ahead does the job here. We could do self-IPI on platforms that have an SMP-capable interrupt controller too but it would probably have higher overhead and would require verifying that the code for each of our different interrupt controllers is safe to be called from NMIs (hint: ioremap space isn't safe to access from NMIs for us on some CPU families...). We might be able to do better than using the decrementer on some CPUs by using local doorbells, but for now this will do. > I thought well that's what powerpc was doing for irq work but I wasn't > sure I understood the code correctly. I should have pinged people > about that, sorry. No worries, Cheers, Ben.