From patchwork Tue Nov 24 15:50:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 11929277 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3623DC63777 for ; Tue, 24 Nov 2020 15:53:22 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 BB4AB206F7 for ; Tue, 24 Nov 2020 15:53:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ZnvfVXN9"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="uALVM0o5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BB4AB206F7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version: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=JLoHlZIbXZpku0pfDHwYypkyjANmFXjrK3E+JjYkqA4=; b=ZnvfVXN9EzkMSfV91M1aYBrAK LbRx9WcAqTO0B4YAc2z29wlKivbsW7MoOFh7nsZ+7EGjHftOtAA4C99ozNbatyP26RDjrCN2aN+LW gNJOoUYeSsAbXM2vgJ2HF6bAGuoj+knKAma9VHglPdaQNZ8T/BOwL0N7mDeCgmx13w6ZN9xUzQ+r4 s2gdWw7SYy3dabdAm1AMzvjwPz3N6bRaS7CR2TA/Qe/ME2xw4GcavzXvB9vCKLDTErmFZ932TFG/Q E1Pr7PVJLaUaPVOVDDhBxCDHDKS0iaHhF5cwB1kjyQpZriBhrrslz5RdG+V95n8Cb2NX4zQt8nbyZ faMED/YPg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1khacV-0005b7-Nd; Tue, 24 Nov 2020 15:52:43 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1khabL-00053f-O6 for linux-arm-kernel@lists.infradead.org; Tue, 24 Nov 2020 15:51:33 +0000 Received: from localhost.localdomain (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 719FB20715; Tue, 24 Nov 2020 15:51:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606233090; bh=hvH0BE8HcbG7lVb8mNQA+knlFSJMTK3LFJTOseuTpTI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uALVM0o5VTC1bEZE7HljUehIrSGkGIlXnv3WnV39BUUO6g21zUzScbYwWj8iSjxBz vXR7+cB4N/3LL/zD3pg6DPnFILnNi4+Tz+THSfFk/P6ZbFRCR0u2O349UG5N2ky7YC dFb0aZIz9ETLvNWw1xWlUgkrEzcSoKCFavG+23Ns= From: Will Deacon To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v4 10/14] sched: Introduce arch_task_cpu_possible_mask() to limit fallback rq selection Date: Tue, 24 Nov 2020 15:50:35 +0000 Message-Id: <20201124155039.13804-11-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20201124155039.13804-1-will@kernel.org> References: <20201124155039.13804-1-will@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201124_105132_045686_0F75AE06 X-CRM114-Status: GOOD ( 17.01 ) 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, Marc Zyngier , kernel-team@android.com, Vincent Guittot , Juri Lelli , Quentin Perret , Peter Zijlstra , Catalin Marinas , Johannes Weiner , linux-kernel@vger.kernel.org, Qais Yousef , Suren Baghdasaryan , Ingo Molnar , Li Zefan , Greg Kroah-Hartman , Tejun Heo , Will Deacon , Morten Rasmussen Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Asymmetric systems may not offer the same level of userspace ISA support across all CPUs, meaning that some applications cannot be executed by some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do not feature support for 32-bit applications on both clusters. On such a system, we must take care not to migrate a task to an unsupported CPU when forcefully moving tasks in select_fallback_rq() in response to a CPU hot-unplug operation. Introduce an arch_task_cpu_possible_mask() hook which, given a task argument, allows an architecture to return a cpumask of CPUs that are capable of executing that task. The default implementation returns the cpu_possible_mask, since sane machines do not suffer from per-cpu ISA limitations that affect scheduling. The new mask is used when selecting the fallback runqueue as a last resort before forcing a migration to the first active CPU. Reviewed-by: Quentin Perret Signed-off-by: Will Deacon --- kernel/sched/core.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 818c8f7bdf2a..99992d0beb65 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1696,6 +1696,11 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) #ifdef CONFIG_SMP +/* Must contain at least one active CPU */ +#ifndef arch_task_cpu_possible_mask +#define arch_task_cpu_possible_mask(p) cpu_possible_mask +#endif + /* * Per-CPU kthreads are allowed to run on !active && online CPUs, see * __set_cpus_allowed_ptr() and select_fallback_rq(). @@ -1708,7 +1713,10 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) if (is_per_cpu_kthread(p)) return cpu_online(cpu); - return cpu_active(cpu); + if (!cpu_active(cpu)) + return false; + + return cpumask_test_cpu(cpu, arch_task_cpu_possible_mask(p)); } /* @@ -2361,10 +2369,9 @@ static int select_fallback_rq(int cpu, struct task_struct *p) } fallthrough; case possible: - do_set_cpus_allowed(p, cpu_possible_mask); + do_set_cpus_allowed(p, arch_task_cpu_possible_mask(p)); state = fail; break; - case fail: BUG(); break;