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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 9AEFCC76186 for ; Wed, 17 Jul 2019 08:44:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7609D2173E for ; Wed, 17 Jul 2019 08:44:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726248AbfGQIoD (ORCPT ); Wed, 17 Jul 2019 04:44:03 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:52527 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725890AbfGQIoC (ORCPT ); Wed, 17 Jul 2019 04:44:02 -0400 Received: from pd9ef1cb8.dip0.t-ipconnect.de ([217.239.28.184] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1hnfXc-0000rM-8D; Wed, 17 Jul 2019 10:44:00 +0200 Date: Wed, 17 Jul 2019 10:43:59 +0200 (CEST) From: Thomas Gleixner To: LAK cc: LKML , Catalin Marinas , Will Deacon , Peter Zijlstra Subject: [PATCH] arm64: Avoid pointless schedule_preempt_irq() invocations Message-ID: User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When preempt_count is zero on return from interrupt then schedule_preempt_irq() is invoked even if TIF_NEED_RESCHED is not set. That does not make sense because schedule_preempt_irq() has to go through a full __schedule() for nothing in that case. Check TIF_NEED_RESCHED and invoke schedule_preempt_irq() only if set. Signed-off-by: Thomas Gleixner --- Found while staring at some RT wrecakge in that area. --- arch/arm64/kernel/entry.S | 4 ++++ 1 file changed, 4 insertions(+) --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -680,6 +680,10 @@ alternative_if ARM64_HAS_IRQ_PRIO_MASKIN orr x24, x24, x0 alternative_else_nop_endif cbnz x24, 1f // preempt count != 0 || NMI return path + + ldr x0, [tsk, #TSK_TI_FLAGS] // get flags + tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling? + bl preempt_schedule_irq // irq en/disable is done inside 1: #endif