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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 52756C433E1 for ; Thu, 20 Aug 2020 09:41:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 28F1C20885 for ; Thu, 20 Aug 2020 09:41:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597916502; bh=y95aqhMghBTuYzwc96pgSXwzVNjO3rBpSfMV1LhH2hg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=KiGJ0cf6s9DWarjpXbGVupcUUsGZkFPJUdMI+dWm0myrTIMF4/AvdiGLUG4sc5hSN Ymfb//NlwtsxFhBkCYQBQjq/Q9n6GXeVsH813Ackpm7pTPd4ECkYuV//Vcut6g9vkH 0xjMWCrGgKyL5atiwlzDqNA6rdEv+pSaUBBYIlT0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729104AbgHTJlj (ORCPT ); Thu, 20 Aug 2020 05:41:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:35030 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728307AbgHTJla (ORCPT ); Thu, 20 Aug 2020 05:41:30 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id F1F4C207DE; Thu, 20 Aug 2020 09:41:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597916490; bh=y95aqhMghBTuYzwc96pgSXwzVNjO3rBpSfMV1LhH2hg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=u0uMQBOEX3afTNZx8sX8TpDlzk73i9K++eSxJJR00+j/nsZMVl1tbJS0JSXddWUwS v1onKzTydz0wUjhnVonA66dbniTws1YXt0TQhaSyibuZsBo9QwIoKleHaWVtuM4fRG rWuRV/LEOn23eXZdu94iR0ThIcx5T5N3p9cbhHBQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Qais Yousef , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 5.7 146/204] sched/uclamp: Fix a deadlock when enabling uclamp static key Date: Thu, 20 Aug 2020 11:20:43 +0200 Message-Id: <20200820091613.539576056@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200820091606.194320503@linuxfoundation.org> References: <20200820091606.194320503@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Qais Yousef [ Upstream commit e65855a52b479f98674998cb23b21ef5a8144b04 ] The following splat was caught when setting uclamp value of a task: BUG: sleeping function called from invalid context at ./include/linux/percpu-rwsem.h:49 cpus_read_lock+0x68/0x130 static_key_enable+0x1c/0x38 __sched_setscheduler+0x900/0xad8 Fix by ensuring we enable the key outside of the critical section in __sched_setscheduler() Fixes: 46609ce22703 ("sched/uclamp: Protect uclamp fast path code with static key") Signed-off-by: Qais Yousef Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200716110347.19553-4-qais.yousef@arm.com Signed-off-by: Sasha Levin --- kernel/sched/core.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 49b5c5cf9271d..ebecf1cc3b788 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1248,6 +1248,15 @@ static int uclamp_validate(struct task_struct *p, if (upper_bound > SCHED_CAPACITY_SCALE) return -EINVAL; + /* + * We have valid uclamp attributes; make sure uclamp is enabled. + * + * We need to do that here, because enabling static branches is a + * blocking operation which obviously cannot be done while holding + * scheduler locks. + */ + static_branch_enable(&sched_uclamp_used); + return 0; } @@ -1278,8 +1287,6 @@ static void __setscheduler_uclamp(struct task_struct *p, if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP))) return; - static_branch_enable(&sched_uclamp_used); - if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) { uclamp_se_set(&p->uclamp_req[UCLAMP_MIN], attr->sched_util_min, true); -- 2.25.1