From mboxrd@z Thu Jan 1 00:00:00 1970 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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 94367C2BA83 for ; Fri, 14 Feb 2020 15:26:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 63CA1217F4 for ; Fri, 14 Feb 2020 15:26:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581693994; bh=KYwPMvDEV3XtBM2fDFyocr2Ioaq9g5FNtGjGvxMoPUo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=CGh8vzlp1/16DXM6YOQmS9f5cmWoPLe6gclmNk+8B9zNLScfRCQCjO7J+Jr0pVmXQ kzDHRUxfPX+nooIeYFyCaVrb4hysm1u9u1y7FpQYZZ9vFylgt6ur2i8jQv9LeOnm/K R/n9ewnyZl7JkDbv7ns+/OfBMndfTTHZBI9p3gIw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387491AbgBNP0d (ORCPT ); Fri, 14 Feb 2020 10:26:33 -0500 Received: from mail.kernel.org ([198.145.29.99]:38238 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729412AbgBNP0b (ORCPT ); Fri, 14 Feb 2020 10:26:31 -0500 Received: from lenoir.home (lfbn-ncy-1-985-231.w90-101.abo.wanadoo.fr [90.101.63.231]) (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 A4F5724654; Fri, 14 Feb 2020 15:26:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581693990; bh=KYwPMvDEV3XtBM2fDFyocr2Ioaq9g5FNtGjGvxMoPUo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uv3tsM20Sr6r9orNWjQokYf3Jt1kCrHCJAPFLbHWU/YfOXhQ4ZHCFPnVx4YT4GCm/ YK++KMP3PNIQFFLPbeg8ldokmoOBguk2Al0UO1GAq7pRTQRwMIQVbhjZ3H7FMk2UJd HsmUbBHga3MrDEkuRUJgRU2WWSXw7n8r7X21fklo= From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Paul Burton , Peter Zijlstra , "David S . Miller" , Borislav Petkov , Benjamin Herrenschmidt , Paul Mackerras , Thomas Gleixner , Andy Lutomirski , Ralf Baechle , Ingo Molnar , Will Deacon , Catalin Marinas , Michael Ellerman , Russell King Subject: [PATCH 2/5] context-tracking: Introduce CONFIG_HAVE_TIF_NOHZ Date: Fri, 14 Feb 2020 16:26:12 +0100 Message-Id: <20200214152615.25447-3-frederic@kernel.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200214152615.25447-1-frederic@kernel.org> References: <20200214152615.25447-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A few archs (x86, arm, arm64) don't rely anymore on TIF_NOHZ to call into context tracking on user entry/exit but instead use static keys (or not) to optimize those calls. Ideally every arch should migrate to that behaviour in the long run. Settle a config option to let those archs remove their TIF_NOHZ definitions. Signed-off-by: Frederic Weisbecker Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Andy Lutomirski Cc: Russell King Cc: Catalin Marinas Cc: Will Deacon Cc: Ralf Baechle Cc: Paul Burton Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: David S. Miller --- arch/Kconfig | 16 +++++++++++----- arch/arm/Kconfig | 1 + arch/arm64/Kconfig | 1 + arch/mips/Kconfig | 1 + arch/powerpc/Kconfig | 1 + arch/sparc/Kconfig | 1 + arch/x86/Kconfig | 1 + kernel/context_tracking.c | 2 ++ 8 files changed, 19 insertions(+), 5 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 98de654b79b3..dbf420a9f87b 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -540,11 +540,17 @@ config HAVE_CONTEXT_TRACKING help Provide kernel/user boundaries probes necessary for subsystems that need it, such as userspace RCU extended quiescent state. - Syscalls need to be wrapped inside user_exit()-user_enter() through - the slow path using TIF_NOHZ flag. Exceptions handlers must be - wrapped as well. Irqs are already protected inside - rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on - irq exit still need to be protected. + Syscalls need to be wrapped inside user_exit()-user_enter(), either + optimized behind static key or through the slow path using TIF_NOHZ + flag. Exceptions handlers must be wrapped as well. Irqs are already + protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal + handling on irq exit still need to be protected. + +config HAVE_TIF_NOHZ + bool + help + Arch relies on TIF_NOHZ and syscall slow path to implement context + tracking calls to user_enter()/user_exit(). config HAVE_VIRT_CPU_ACCOUNTING bool diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 97864aabc2a6..38b764cae559 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -72,6 +72,7 @@ config ARM select HAVE_ARM_SMCCC if CPU_V7 select HAVE_EBPF_JIT if !CPU_ENDIAN_BE32 select HAVE_CONTEXT_TRACKING + select HAVE_TIF_NOHZ select HAVE_COPY_THREAD_TLS select HAVE_C_RECORDMCOUNT select HAVE_DEBUG_KMEMLEAK if !XIP_KERNEL diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 0b30e884e088..5c945fa3df26 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -140,6 +140,7 @@ config ARM64 select HAVE_CMPXCHG_DOUBLE select HAVE_CMPXCHG_LOCAL select HAVE_CONTEXT_TRACKING + select HAVE_TIF_NOHZ select HAVE_COPY_THREAD_TLS select HAVE_DEBUG_BUGVERBOSE select HAVE_DEBUG_KMEMLEAK diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index 797d7f1ad5fe..2589d4760e45 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -51,6 +51,7 @@ config MIPS select HAVE_ASM_MODVERSIONS select HAVE_CBPF_JIT if !64BIT && !CPU_MICROMIPS select HAVE_CONTEXT_TRACKING + select HAVE_TIF_NOHZ select HAVE_COPY_THREAD_TLS select HAVE_C_RECORDMCOUNT select HAVE_DEBUG_KMEMLEAK diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 497b7d0b2d7e..6f40af294685 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -182,6 +182,7 @@ config PPC select HAVE_STACKPROTECTOR if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13) select HAVE_STACKPROTECTOR if PPC32 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r2) select HAVE_CONTEXT_TRACKING if PPC64 + select HAVE_TIF_NOHZ if PPC64 select HAVE_COPY_THREAD_TLS select HAVE_DEBUG_KMEMLEAK select HAVE_DEBUG_STACKOVERFLOW diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig index c1dd6dd642f4..9cc9ab04bd99 100644 --- a/arch/sparc/Kconfig +++ b/arch/sparc/Kconfig @@ -71,6 +71,7 @@ config SPARC64 select HAVE_FTRACE_MCOUNT_RECORD select HAVE_SYSCALL_TRACEPOINTS select HAVE_CONTEXT_TRACKING + select HAVE_TIF_NOHZ select HAVE_DEBUG_KMEMLEAK select IOMMU_HELPER select SPARSE_IRQ diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index beea77046f9b..549eed3460c9 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -211,6 +211,7 @@ config X86 select HAVE_STACK_VALIDATION if X86_64 select HAVE_RSEQ select HAVE_SYSCALL_TRACEPOINTS + select HAVE_TIF_NOHZ if X86_64 select HAVE_UNSTABLE_SCHED_CLOCK select HAVE_USER_RETURN_NOTIFIER select HAVE_GENERIC_VDSO diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 0296b4bda8f1..ce430885c26c 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -198,11 +198,13 @@ void __init context_tracking_cpu_set(int cpu) if (initialized) return; +#ifdef CONFIG_HAVE_TIF_NOHZ /* * Set TIF_NOHZ to init/0 and let it propagate to all tasks through fork * This assumes that init is the only task at this early boot stage. */ set_tsk_thread_flag(&init_task, TIF_NOHZ); +#endif WARN_ON_ONCE(!tasklist_empty()); initialized = true; -- 2.25.0