From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH V2 16/19] csky: SMP support Date: Thu, 5 Jul 2018 20:05:03 +0200 Message-ID: <20180705180503.GH2530@hirez.programming.kicks-ass.net> References: <21d859826fe19aecaa2aefe3103d6d33e6f1b925.1530465326.git.ren_guo@c-sky.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <21d859826fe19aecaa2aefe3103d6d33e6f1b925.1530465326.git.ren_guo@c-sky.com> Sender: linux-kernel-owner@vger.kernel.org To: Guo Ren Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, daniel.lezcano@linaro.org, jason@lakedaemon.net, arnd@arndb.de, c-sky_gcc_upstream@c-sky.com, gnu-csky@mentor.com, thomas.petazzoni@bootlin.com, wbx@uclibc-ng.org, green.hu@gmail.com List-Id: linux-arch.vger.kernel.org On Mon, Jul 02, 2018 at 01:30:19AM +0800, Guo Ren wrote: > +static irqreturn_t handle_ipi(int irq, void *dev) > +{ > + unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits; > + > + while (true) { > + unsigned long ops; > + > + /* Order bit clearing and data access. */ > + mb(); > + > + ops = xchg(pending_ipis, 0); > + if (ops == 0) > + return IRQ_HANDLED; > + > + if (ops & (1 << IPI_RESCHEDULE)) > + scheduler_ipi(); > + > + if (ops & (1 << IPI_CALL_FUNC)) > + generic_smp_call_function_interrupt(); > + > + BUG_ON((ops >> IPI_MAX) != 0); > + > + /* Order data access and bit testing. */ > + mb(); > + } > + > + return IRQ_HANDLED; > +} > + > +static void (*send_arch_ipi)(const unsigned long *mask, unsigned long irq) = NULL; > + > +void __init set_send_ipi(void (*func)(const unsigned long *, unsigned long)) > +{ > + if (send_arch_ipi) > + return; > + > + send_arch_ipi = func; > +} > + > +static void > +send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation) > +{ > + int i; > + > + mb(); > + for_each_cpu(i, to_whom) > + set_bit(operation, &ipi_data[i].bits); > + > + mb(); > + send_arch_ipi(cpumask_bits(to_whom), IPI_IRQ); > +} Please explain those mb()'s... I'm thinking you meant to use smp_mb(). But then for handle_ipi(), the xchg() should already imply all those. And the send_ipi_message() only needs the second. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from merlin.infradead.org ([205.233.59.134]:58330 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753405AbeGESFt (ORCPT ); Thu, 5 Jul 2018 14:05:49 -0400 Date: Thu, 5 Jul 2018 20:05:03 +0200 From: Peter Zijlstra Subject: Re: [PATCH V2 16/19] csky: SMP support Message-ID: <20180705180503.GH2530@hirez.programming.kicks-ass.net> References: <21d859826fe19aecaa2aefe3103d6d33e6f1b925.1530465326.git.ren_guo@c-sky.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <21d859826fe19aecaa2aefe3103d6d33e6f1b925.1530465326.git.ren_guo@c-sky.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Guo Ren Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, daniel.lezcano@linaro.org, jason@lakedaemon.net, arnd@arndb.de, c-sky_gcc_upstream@c-sky.com, gnu-csky@mentor.com, thomas.petazzoni@bootlin.com, wbx@uclibc-ng.org, green.hu@gmail.com Message-ID: <20180705180503.AQa7jtg1lgiwganV4uNphzz876rZugMmVleDGaHKVjM@z> On Mon, Jul 02, 2018 at 01:30:19AM +0800, Guo Ren wrote: > +static irqreturn_t handle_ipi(int irq, void *dev) > +{ > + unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits; > + > + while (true) { > + unsigned long ops; > + > + /* Order bit clearing and data access. */ > + mb(); > + > + ops = xchg(pending_ipis, 0); > + if (ops == 0) > + return IRQ_HANDLED; > + > + if (ops & (1 << IPI_RESCHEDULE)) > + scheduler_ipi(); > + > + if (ops & (1 << IPI_CALL_FUNC)) > + generic_smp_call_function_interrupt(); > + > + BUG_ON((ops >> IPI_MAX) != 0); > + > + /* Order data access and bit testing. */ > + mb(); > + } > + > + return IRQ_HANDLED; > +} > + > +static void (*send_arch_ipi)(const unsigned long *mask, unsigned long irq) = NULL; > + > +void __init set_send_ipi(void (*func)(const unsigned long *, unsigned long)) > +{ > + if (send_arch_ipi) > + return; > + > + send_arch_ipi = func; > +} > + > +static void > +send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation) > +{ > + int i; > + > + mb(); > + for_each_cpu(i, to_whom) > + set_bit(operation, &ipi_data[i].bits); > + > + mb(); > + send_arch_ipi(cpumask_bits(to_whom), IPI_IRQ); > +} Please explain those mb()'s... I'm thinking you meant to use smp_mb(). But then for handle_ipi(), the xchg() should already imply all those. And the send_ipi_message() only needs the second.