From patchwork Tue Oct 27 13:47:03 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 289891 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=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 AC388C55178 for ; Tue, 27 Oct 2020 14:55:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 50F9822281 for ; Tue, 27 Oct 2020 14:55:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603810515; bh=83pEo1S7D1IwnxpOqE7t6gjf+YFk9V8DIqqxSYYN6Hk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=XeH5Mxr6ZV8xd6sLmZTA4R6BpY/GK3VOv5BfnWHmv4mOeUlKbNEX4rW/RfWZ2s8Su S1X14u1hWTLoudyF8vogvIFwdW7FACarxP8fObPpzR+RLtUEdURGzkCTEv4t9jM+V1 6LgCRPw3DSScBJzKaQgnnCJRjBGorJ6dn7lgFCbQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752542AbgJ0OzG (ORCPT ); Tue, 27 Oct 2020 10:55:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:52604 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1740625AbgJ0Owk (ORCPT ); Tue, 27 Oct 2020 10:52:40 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 D62BD20773; Tue, 27 Oct 2020 14:52:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603810358; bh=83pEo1S7D1IwnxpOqE7t6gjf+YFk9V8DIqqxSYYN6Hk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=S+suT2qufEQmfHKSrdrkKpkoxdNVfKj+pVYhjk1MXmv2HvscLv9GC4nRjmRyfWDEP aXwwVfz0Z7FLhGBzn0jATyAoLMaVKi2lraILJwryNoj3qS+W3/JMlLr5O2KTQAboEI m+t/9xKH+MKER8hl3GZUJocLUaUG9EpWbrh59JZ8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lukasz Luba , "Peter Zijlstra (Intel)" , Valentin Schneider , Sasha Levin Subject: [PATCH 5.8 080/633] sched/fair: Fix wrong negative conversion in find_energy_efficient_cpu() Date: Tue, 27 Oct 2020 14:47:03 +0100 Message-Id: <20201027135526.447517817@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135522.655719020@linuxfoundation.org> References: <20201027135522.655719020@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Lukasz Luba [ Upstream commit da0777d35f47892f359c3f73ea155870bb595700 ] In find_energy_efficient_cpu() 'cpu_cap' could be less that 'util'. It might be because of RT, DL (so higher sched class than CFS), irq or thermal pressure signal, which reduce the capacity value. In such situation the result of 'cpu_cap - util' might be negative but stored in the unsigned long. Then it might be compared with other unsigned long when uclamp_rq_util_with() reduced the 'util' such that is passes the fits_capacity() check. Prevent this situation and make the arithmetic more safe. Fixes: 1d42509e475cd ("sched/fair: Make EAS wakeup placement consider uclamp restrictions") Signed-off-by: Lukasz Luba Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Link: https://lkml.kernel.org/r/20200810083004.26420-1-lukasz.luba@arm.com Signed-off-by: Sasha Levin --- kernel/sched/fair.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 6b3b59cc51d6c..f71e8b0e0346a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6586,7 +6586,8 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) util = cpu_util_next(cpu, p, cpu); cpu_cap = capacity_of(cpu); - spare_cap = cpu_cap - util; + spare_cap = cpu_cap; + lsub_positive(&spare_cap, util); /* * Skip CPUs that cannot satisfy the capacity request.