From patchwork Fri Sep 13 18:19:42 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cristian Marussi X-Patchwork-Id: 11145059 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7A2F7912 for ; Fri, 13 Sep 2019 18:21:11 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 57B9B214D8 for ; Fri, 13 Sep 2019 18:21:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="aA1y+Yoa" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 57B9B214D8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=Oxb/icvyYAtgtPn5hvULwPNT83gA/6zjcYJuoP7XVDg=; b=aA1y+YoarQiquHdR9N9IRCU2Hi sfLJ2ycs+z/g1PMmiRW1drY7mW/JrFMyRrayc4QGvb4hF7wC8q3SWqsiWUGy3bw1kaZfSnTITrmPT A5Y6hYti5eDILjCckTTfrnhTLNNBuNMitNGRLpkABp0hskV23ejCEvh6xpPflvlZH4Vlpztl3Rw7q 0IA9D9zwG4r5xNX3BMg+me248ZjQcEgBEpoZvcpsoHb0VSFxArBJNvl8ikocMIDW5CX5qpZYe602F 5/JXdZzRu/RHPMM3AdDGyt1jzRRFWNWmTXNSsTXugbUtazES9sPb1bkuApM6CXCuFCtVhNh6cMcHa YpElp7Xw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1i8qBt-0005C5-S8; Fri, 13 Sep 2019 18:21:05 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1i8qBc-0004vF-FE for linux-arm-kernel@lists.infradead.org; Fri, 13 Sep 2019 18:20:50 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C3D401570; Fri, 13 Sep 2019 11:20:47 -0700 (PDT) Received: from e120937-lin.cambridge.arm.com (e120937-lin.cambridge.arm.com [10.1.197.50]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5644C3F71F; Fri, 13 Sep 2019 11:20:45 -0700 (PDT) From: Cristian Marussi To: linux-kernel@vger.kernel.org Subject: [RFC PATCH v2 01/12] smp: add generic SMP-stop support to common code Date: Fri, 13 Sep 2019 19:19:42 +0100 Message-Id: <20190913181953.45748-2-cristian.marussi@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190913181953.45748-1-cristian.marussi@arm.com> References: <20190913181953.45748-1-cristian.marussi@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190913_112048_595134_97AA2516 X-CRM114-Status: GOOD ( 19.01 ) X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, mark.rutland@arm.com, sparclinux@vger.kernel.org, dzickus@redhat.com, ehabkost@redhat.com, peterz@infradead.org, catalin.marinas@arm.com, x86@kernel.org, linux@armlinux.org.uk, davem@davemloft.net, hch@infradead.org, takahiro.akashi@linaro.org, mingo@redhat.com, james.morse@arm.com, hidehiro.kawai.ez@hitachi.com, tglx@linutronix.de, will@kernel.org, dave.martin@arm.com, linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org There was a lot of code duplication across architectures regarding the SMP stop procedures' logic; moreover some of this duplicated code logic happened to be similarly faulty across a few architectures: while fixing such logic, move such generic logic as much as possible inside common code. Collect all the common logic related to SMP stop operations into the common SMP code; any architecture willing to use such centralized logic can select CONFIG_ARCH_USE_COMMON_STOP=y and provide the related arch-specific helpers: in such a scenario, those architectures will transparently start using the common code provided by smp_send_stop() common function. On the other side, Architectures not willing to use common code SMP stop logic will simply leave CONFIG_ARCH_USE_COMMON_STOP undefined and carry on executing their local arch-specific smp_send_stop() as before. Suggested-by: Dave Martin Signed-off-by: Cristian Marussi --- v1 --> v2 - moved related Kconfig to common code inside arch/Kconfig - introduced additional CONFIG_USE_COMMON_STOP selected by CONFIG_ARCH_USE_COMMON_STOP - introduced helpers to let architectures optionally alter the default common code behaviour while waiting for CPUs: change timeout or wait for ever. (will be needed by x86) --- arch/Kconfig | 7 +++++ include/linux/smp.h | 55 +++++++++++++++++++++++++++++++++++++ kernel/smp.c | 67 +++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 129 insertions(+) diff --git a/arch/Kconfig b/arch/Kconfig index a7b57dd42c26..89766e6c0ac8 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -166,6 +166,13 @@ config ARCH_USE_BUILTIN_BSWAP instructions should set this. And it shouldn't hurt to set it on architectures that don't have such instructions. +config ARCH_USE_COMMON_SMP_STOP + def_bool n + +config USE_COMMON_SMP_STOP + depends on SMP && ARCH_USE_COMMON_SMP_STOP + def_bool y + config KRETPROBES def_bool y depends on KPROBES && HAVE_KRETPROBES diff --git a/include/linux/smp.h b/include/linux/smp.h index 6fc856c9eda5..381a14bfcd96 100644 --- a/include/linux/smp.h +++ b/include/linux/smp.h @@ -77,6 +77,61 @@ int smp_call_function_single_async(int cpu, call_single_data_t *csd); */ extern void smp_send_stop(void); +#ifdef CONFIG_USE_COMMON_SMP_STOP +static atomic_t wait_forever; +static atomic_t wait_timeout = ATOMIC_INIT(USEC_PER_SEC); + +/* + * An Architecture can optionally decide to use this helper to change the + * waiting behaviour of common STOP logic, forcing to wait forever for + * all CPUs to be stopped. + */ +static inline void smp_stop_set_wait_forever(int wait) +{ + atomic_set(&wait_forever, wait); + /* ensure wait atomic-op is visible */ + smp_mb__after_atomic(); +} + +/* + * An Architecture can optionally decide to use this helper to change the + * waiting timeout of common STOP logic. A ZERO timeout means no timeout + * at all as long as wait_forever was not previously set. + * + * Note that wait_forever and timeout must remain individually selectable: + * so you can temporarily request wait_forever while keeping the same timeout + * settings. + */ +static inline void smp_stop_set_wait_timeout_us(unsigned long timeout) +{ + atomic_set(&wait_timeout, timeout); + /* ensure timeout atomic-op is visible */ + smp_mb__after_atomic(); +} + +/* Retrieve the current wait settings. */ +static inline bool smp_stop_get_wait_timeout_us(unsigned long *timeout) +{ + if (timeout) + *timeout = atomic_read(&wait_timeout); + return atomic_read(&wait_forever); +} + +/* + * Any Architecture willing to use STOP common logic implementation + * MUST at least provide the arch_smp_stop_call() helper which is in + * charge of its own arch-specific CPU-stop mechanism. + */ +extern void arch_smp_stop_call(cpumask_t *cpus); + +/* + * An Architecture CAN also provide the arch_smp_cpus_stop_complete() + * dedicated helper, to perform any final arch-specific operation on + * the local CPU once the other CPUs have been successfully stopped. + */ +void arch_smp_cpus_stop_complete(void); +#endif + /* * sends a 'reschedule' event to another CPU: */ diff --git a/kernel/smp.c b/kernel/smp.c index 7dbcb402c2fc..72f99bf13fd0 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -20,6 +20,7 @@ #include #include #include +#include #include "smpboot.h" @@ -817,3 +818,69 @@ int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys) return sscs.ret; } EXPORT_SYMBOL_GPL(smp_call_on_cpu); + +#ifdef CONFIG_USE_COMMON_SMP_STOP +void __weak arch_smp_cpus_stop_complete(void) { } + +static inline bool any_other_cpus_online(cpumask_t *mask, + unsigned int this_cpu_id) +{ + cpumask_copy(mask, cpu_online_mask); + cpumask_clear_cpu(this_cpu_id, mask); + + return !cpumask_empty(mask); +} + +/* + * This centralizes the common logic to: + * + * - evaluate which CPUs are online and needs to be notified for stop, + * while considering properly the status of the calling CPU + * + * - call the arch-specific helpers to request the effective stop + * + * - wait for the stop operation to be completed across all involved CPUs + * monitoring the cpu_online_mask + */ +void smp_send_stop(void) +{ + unsigned int this_cpu_id; + cpumask_t mask; + + this_cpu_id = smp_processor_id(); + if (any_other_cpus_online(&mask, this_cpu_id)) { + bool wait; + unsigned long timeout; + unsigned int this_cpu_online = cpu_online(this_cpu_id); + + if (system_state <= SYSTEM_RUNNING) + pr_crit("stopping secondary CPUs\n"); + arch_smp_stop_call(&mask); + + /* + * Defaults to wait up to one second for other CPUs to stop; + * architectures can modify the default timeout or request + * to wait forever. + * + * Here we rely simply on cpu_online_mask to sync with + * arch-specific stop code without bloating the code with an + * additional atomic_t ad-hoc counter. + * + * As a consequence we'll need proper explicit memory barriers + * in case the other CPUs running the arch-specific stop-code + * would need to commit to memory some data (like saved_regs). + */ + wait = smp_stop_get_wait_timeout_us(&timeout); + while (num_online_cpus() > this_cpu_online && + (wait || timeout--)) + udelay(1); + /* ensure any stopping-CPUs memory access is made visible */ + smp_rmb(); + if (num_online_cpus() > this_cpu_online) + pr_warn("failed to stop secondary CPUs %*pbl\n", + cpumask_pr_args(cpu_online_mask)); + } + /* Perform final (possibly arch-specific) work on this CPU */ + arch_smp_cpus_stop_complete(); +} +#endif