From nobody Wed Dec 17 05:50:43 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A640C4167B for ; Wed, 29 Nov 2023 15:08:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234999AbjK2Ozz (ORCPT ); Wed, 29 Nov 2023 09:55:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32774 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234958AbjK2Ozv (ORCPT ); Wed, 29 Nov 2023 09:55:51 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2EDD0BE; Wed, 29 Nov 2023 06:55:57 -0800 (PST) Date: Wed, 29 Nov 2023 14:55:55 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701269755; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Nt6Krllh0mQwdWox8Qj0Ef6jN+mnzfU9kFcSAETUC3o=; b=gq715mBss1D6hmeL9Dlxv4hcDsX5oQhPUeffKyl7NI3SZJjd+WE5gOOhhML8Ws/J5m8b8k huxBHjcjpFYRzyt1Gznf0jRJV/Ce8ygg/GYT+cwVERhYJLs8s7YTDyHQqhbF9ASB1er7qz 1uXXnKuShFs2jFj4crtjmHB4li8zh1bBk+ZPajJzdlgb6yWShrpU17eEmhn11y+jlFyyV3 NMiZWdFkny0bA6vKnSxaRDdx2ytPO/lX3Sttf42GBpsoe7tvSWEMQMXu7W3LetQo8BbMLS VzgjBWcApUjgByh34m0EoAU6+qTP/1qS4c1WOrKGvIilax9GgJ6FMg/BjNGACQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701269755; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Nt6Krllh0mQwdWox8Qj0Ef6jN+mnzfU9kFcSAETUC3o=; b=S+lft88A0i7CNT3TInDWp/o1ZXDcrkSCuK5KvDQ0JXgywnMgrYBzEEjqIaUYln/iUUk0u+ 7Ug0s4lj0PMDptAw== From: "tip-bot2 for Peter Zijlstra" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/core] x86: Fix CPUIDLE_FLAG_IRQ_ENABLE leaking timer reprogram Cc: "Peter Zijlstra (Intel)" , Frederic Weisbecker , "Rafael J. Wysocki" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20231115151325.6262-3-frederic@kernel.org> References: <20231115151325.6262-3-frederic@kernel.org> MIME-Version: 1.0 Message-ID: <170126975511.398.12493947150541739641.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/core branch of tip: Commit-ID: edc8fc01f608108b0b7580cb2c29dfb5135e5f0e Gitweb: https://git.kernel.org/tip/edc8fc01f608108b0b7580cb2c29dfb51= 35e5f0e Author: Peter Zijlstra AuthorDate: Wed, 15 Nov 2023 10:13:23 -05:00 Committer: Peter Zijlstra CommitterDate: Wed, 29 Nov 2023 15:44:01 +01:00 x86: Fix CPUIDLE_FLAG_IRQ_ENABLE leaking timer reprogram intel_idle_irq() re-enables IRQs very early. As a result, an interrupt may fire before mwait() is eventually called. If such an interrupt queues a timer, it may go unnoticed until mwait returns and the idle loop handles the tick re-evaluation. And monitoring TIF_NEED_RESCHED doesn't help because a local timer enqueue doesn't set that flag. The issue is mitigated by the fact that this idle handler is only invoked for shallow C-states when, presumably, the next tick is supposed to be close enough. There may still be rare cases though when the next tick is far away and the selected C-state is shallow, resulting in a timer getting ignored for a while. Fix this with using sti_mwait() whose IRQ-reenablement only triggers upon calling mwait(), dealing with the race while keeping the interrupt latency within acceptable bounds. Fixes: c227233ad64c (intel_idle: enable interrupts before C1 on Xeons) Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Acked-by: Rafael J. Wysocki Link: https://lkml.kernel.org/r/20231115151325.6262-3-frederic@kernel.org --- arch/x86/include/asm/mwait.h | 11 +++++++++-- drivers/idle/intel_idle.c | 19 +++++++------------ 2 files changed, 16 insertions(+), 14 deletions(-) diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h index 341ee4f..920426d 100644 --- a/arch/x86/include/asm/mwait.h +++ b/arch/x86/include/asm/mwait.h @@ -124,8 +124,15 @@ static __always_inline void mwait_idle_with_hints(unsi= gned long eax, unsigned lo } =20 __monitor((void *)¤t_thread_info()->flags, 0, 0); - if (!need_resched()) - __mwait(eax, ecx); + + if (!need_resched()) { + if (ecx & 1) { + __mwait(eax, ecx); + } else { + __sti_mwait(eax, ecx); + raw_local_irq_disable(); + } + } } current_clr_polling(); } diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index dcda0af..3e01a6b 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -131,11 +131,12 @@ static unsigned int mwait_substates __initdata; #define MWAIT2flg(eax) ((eax & 0xFF) << 24) =20 static __always_inline int __intel_idle(struct cpuidle_device *dev, - struct cpuidle_driver *drv, int index) + struct cpuidle_driver *drv, + int index, bool irqoff) { struct cpuidle_state *state =3D &drv->states[index]; unsigned long eax =3D flg2MWAIT(state->flags); - unsigned long ecx =3D 1; /* break on interrupt flag */ + unsigned long ecx =3D 1*irqoff; /* break on interrupt flag */ =20 mwait_idle_with_hints(eax, ecx); =20 @@ -159,19 +160,13 @@ static __always_inline int __intel_idle(struct cpuidl= e_device *dev, static __cpuidle int intel_idle(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { - return __intel_idle(dev, drv, index); + return __intel_idle(dev, drv, index, true); } =20 static __cpuidle int intel_idle_irq(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { - int ret; - - raw_local_irq_enable(); - ret =3D __intel_idle(dev, drv, index); - raw_local_irq_disable(); - - return ret; + return __intel_idle(dev, drv, index, false); } =20 static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev, @@ -184,7 +179,7 @@ static __cpuidle int intel_idle_ibrs(struct cpuidle_dev= ice *dev, if (smt_active) __update_spec_ctrl(0); =20 - ret =3D __intel_idle(dev, drv, index); + ret =3D __intel_idle(dev, drv, index, true); =20 if (smt_active) __update_spec_ctrl(spec_ctrl); @@ -196,7 +191,7 @@ static __cpuidle int intel_idle_xstate(struct cpuidle_d= evice *dev, struct cpuidle_driver *drv, int index) { fpu_idle_fpregs(); - return __intel_idle(dev, drv, index); + return __intel_idle(dev, drv, index, true); } =20 /**