From patchwork Wed Aug 11 20:13:51 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Valentin Schneider X-Patchwork-Id: 495518 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,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 EDA37C4338F for ; Wed, 11 Aug 2021 20:14:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CEACE6105A for ; Wed, 11 Aug 2021 20:14:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231892AbhHKUOj (ORCPT ); Wed, 11 Aug 2021 16:14:39 -0400 Received: from foss.arm.com ([217.140.110.172]:57720 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231897AbhHKUOi (ORCPT ); Wed, 11 Aug 2021 16:14:38 -0400 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 4DCC11042; Wed, 11 Aug 2021 13:14:14 -0700 (PDT) Received: from e113632-lin.cambridge.arm.com (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 3C7863F40C; Wed, 11 Aug 2021 13:14:11 -0700 (PDT) From: Valentin Schneider To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, rcu@vger.kernel.org, linux-rt-users@vger.kernel.org Cc: Catalin Marinas , Will Deacon , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Steven Rostedt , Daniel Bristot de Oliveira , Sebastian Andrzej Siewior , "Paul E. McKenney" , Frederic Weisbecker , Josh Triplett , Mathieu Desnoyers , Davidlohr Bueso , Lai Jiangshan , Joel Fernandes , Anshuman Khandual , Vincenzo Frascino , Steven Price , Ard Biesheuvel , Boqun Feng , Mike Galbraith Subject: [PATCH v3 1/4] rcutorture: Don't disable softirqs with preemption disabled when PREEMPT_RT Date: Wed, 11 Aug 2021 21:13:51 +0100 Message-Id: <20210811201354.1976839-2-valentin.schneider@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210811201354.1976839-1-valentin.schneider@arm.com> References: <20210811201354.1976839-1-valentin.schneider@arm.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org Running RCU torture with CONFIG_PREEMPT_RT under v5.14-rc4-rt6 triggers: [ 8.755472] DEBUG_LOCKS_WARN_ON(this_cpu_read(softirq_ctrl.cnt)) [ 8.755482] WARNING: CPU: 1 PID: 137 at kernel/softirq.c:172 __local_bh_disable_ip (kernel/softirq.c:172 (discriminator 31)) [ 8.755500] Modules linked in: [ 8.755506] CPU: 1 PID: 137 Comm: rcu_torture_rea Not tainted 5.14.0-rc4-rt6 #171 [ 8.755514] Hardware name: ARM Juno development board (r0) (DT) [ 8.755518] pstate: 60000005 (nZCv daif -PAN -UAO -TCO BTYPE=--) [ 8.755622] Call trace: [ 8.755624] __local_bh_disable_ip (kernel/softirq.c:172 (discriminator 31)) [ 8.755633] rcutorture_one_extend (kernel/rcu/rcutorture.c:1453) [ 8.755640] rcu_torture_one_read (kernel/rcu/rcutorture.c:1601 kernel/rcu/rcutorture.c:1645) [ 8.755645] rcu_torture_reader (kernel/rcu/rcutorture.c:1737) [ 8.755650] kthread (kernel/kthread.c:327) [ 8.755656] ret_from_fork (arch/arm64/kernel/entry.S:783) [ 8.755663] irq event stamp: 11959 [ 8.755666] hardirqs last enabled at (11959): __rcu_read_unlock (kernel/rcu/tree_plugin.h:695 kernel/rcu/tree_plugin.h:451) [ 8.755675] hardirqs last disabled at (11958): __rcu_read_unlock (kernel/rcu/tree_plugin.h:661 kernel/rcu/tree_plugin.h:451) [ 8.755683] softirqs last enabled at (11950): __local_bh_enable_ip (./arch/arm64/include/asm/irqflags.h:85 kernel/softirq.c:261) [ 8.755692] softirqs last disabled at (11942): rcutorture_one_extend (./include/linux/bottom_half.h:19 kernel/rcu/rcutorture.c:1441) Per this warning, softirqs cannot be disabled in a non-preemptible region under CONFIG_PREEMPT_RT. Adjust RCU torture accordingly. Signed-off-by: Valentin Schneider Acked-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index eecd1caef71d..4f3db1d3170d 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1548,6 +1548,8 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp) * them on non-RT. */ if (IS_ENABLED(CONFIG_PREEMPT_RT)) { + /* Can't disable bh in atomic context under PREEMPT_RT */ + mask &= ~(RCUTORTURE_RDR_ATOM_BH | RCUTORTURE_RDR_ATOM_RBH); /* * Can't release the outermost rcu lock in an irq disabled * section without preemption also being disabled, if irqs From patchwork Wed Aug 11 20:13:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Valentin Schneider X-Patchwork-Id: 495517 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham 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 404B0C432BE for ; Wed, 11 Aug 2021 20:14:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 24AE560462 for ; Wed, 11 Aug 2021 20:14:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232041AbhHKUOt (ORCPT ); Wed, 11 Aug 2021 16:14:49 -0400 Received: from foss.arm.com ([217.140.110.172]:57810 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231953AbhHKUOs (ORCPT ); Wed, 11 Aug 2021 16:14:48 -0400 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 3B867139F; Wed, 11 Aug 2021 13:14:24 -0700 (PDT) Received: from e113632-lin.cambridge.arm.com (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 219433F40C; Wed, 11 Aug 2021 13:14:21 -0700 (PDT) From: Valentin Schneider To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, rcu@vger.kernel.org, linux-rt-users@vger.kernel.org Cc: Catalin Marinas , Will Deacon , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Steven Rostedt , Daniel Bristot de Oliveira , Sebastian Andrzej Siewior , "Paul E. McKenney" , Frederic Weisbecker , Josh Triplett , Mathieu Desnoyers , Davidlohr Bueso , Lai Jiangshan , Joel Fernandes , Anshuman Khandual , Vincenzo Frascino , Steven Price , Ard Biesheuvel , Boqun Feng , Mike Galbraith Subject: [PATCH v3 4/4] arm64: mm: Make arch_faults_on_old_pte() check for migratability Date: Wed, 11 Aug 2021 21:13:54 +0100 Message-Id: <20210811201354.1976839-5-valentin.schneider@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210811201354.1976839-1-valentin.schneider@arm.com> References: <20210811201354.1976839-1-valentin.schneider@arm.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org arch_faults_on_old_pte() relies on the calling context being non-preemptible. CONFIG_PREEMPT_RT turns the PTE lock into a sleepable spinlock, which doesn't disable preemption once acquired, triggering the warning in arch_faults_on_old_pte(). It does however disable migration, ensuring the task remains on the same CPU during the entirety of the critical section, making the read of cpu_has_hw_af() safe and stable. Make arch_faults_on_old_pte() check migratable() instead of preemptible(). Signed-off-by: Valentin Schneider --- arch/arm64/include/asm/pgtable.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index f09bf5c02891..8c0de3234b20 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -995,7 +995,7 @@ static inline void update_mmu_cache(struct vm_area_struct *vma, */ static inline bool arch_faults_on_old_pte(void) { - WARN_ON(preemptible()); + WARN_ON(migratable()); return !cpu_has_hw_af(); }