Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757387AbbBELbA (ORCPT ); Thu, 5 Feb 2015 06:31:00 -0500 Received: from pandora.arm.linux.org.uk ([78.32.30.218]:49986 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751942AbbBELa6 (ORCPT ); Thu, 5 Feb 2015 06:30:58 -0500 Date: Thu, 5 Feb 2015 11:30:47 +0000 From: Russell King - ARM Linux To: Mark Rutland Cc: Krzysztof Kozlowski , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "paulmck@linux.vnet.ibm.com" , Arnd Bergmann , Bartlomiej Zolnierkiewicz , Marek Szyprowski , Stephen Boyd , Catalin Marinas , Will Deacon Subject: Re: [PATCH v2] ARM: Don't use complete() during __cpu_die Message-ID: <20150205113047.GN8656@n2100.arm.linux.org.uk> References: <1423131270-24047-1-git-send-email-k.kozlowski@samsung.com> <20150205105035.GL8656@n2100.arm.linux.org.uk> <20150205112805.GE11344@leverpostej> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150205112805.GE11344@leverpostej> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1863 Lines: 53 On Thu, Feb 05, 2015 at 11:28:05AM +0000, Mark Rutland wrote: > Hi Russell, > > On Thu, Feb 05, 2015 at 10:50:35AM +0000, Russell King - ARM Linux wrote: > > On Thu, Feb 05, 2015 at 11:14:30AM +0100, Krzysztof Kozlowski wrote: > > > The complete() should not be used on offlined CPU. Rewrite the > > > wait-complete mechanism with wait_on_bit_timeout(). > > > > Yuck. > > > > I think that the IPI idea would be far better, and a much smaller patch. > > We can continue using the completions, but instead of running the > > completion on the dying CPU, the dying CPU triggers an IPI which does > > the completion on the requesting CPU. > > This does look _much_ nicer than the bitmask approach. > > [...] > > > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c > > index 194df2f1aa87..c623e27a9c85 100644 > > --- a/arch/arm/kernel/smp.c > > +++ b/arch/arm/kernel/smp.c > > @@ -73,6 +73,9 @@ enum ipi_msg_type { > > IPI_IRQ_WORK, > > IPI_COMPLETION, > > IPI_CPU_BACKTRACE, > > +#ifdef CONFIG_HOTPLUG_CPU > > + IPI_CPU_DEAD, > > +#endif > > }; > > [...] > > > static const char *ipi_types[NR_IPI] __tracepoint_string = { > > #define S(x,s) [x] = s > > S(IPI_WAKEUP, "CPU wakeup interrupts"), > > We'll probably want to add an entry here ("CPU teardown interrupts"?), > and bump NR_IPI in asm/hardirq.h. I'd need to move IPI_CPU_BACKTRACE out of the way then - that'll mostly always be zero (even if the NMI IPI happens.) I'll sort that when I backport the patch to mainline kernels. :) -- FTTC broadband for 0.8mile line: currently at 10.5Mbps 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/