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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0D78AC6FA8E for ; Sun, 26 Feb 2023 03:46:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230093AbjBZDq5 (ORCPT ); Sat, 25 Feb 2023 22:46:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54966 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229982AbjBZDq1 (ORCPT ); Sat, 25 Feb 2023 22:46:27 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A65701715B; Sat, 25 Feb 2023 19:45:54 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 2D57060BF9; Sun, 26 Feb 2023 03:44:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B4CE7C433EF; Sun, 26 Feb 2023 03:44:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1677383075; bh=eHhyE8vPFa3vZFfY8uARa0Kma5ee0m+dhCvW4BTDycg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DKMPkHtXG0Ax4w6Z2tMX8Fvf25aa3u92TvLH77Y9kcCfJ3+Dy57AZFPJbS1UXDD7y Jf+3trK0m3E0V3LDuzbIc4FgL9/vEEuPj0Q50g8Idg++3G4eHtSwaTLbqyiOVD1WVq GWiUBZiPS1KXuEMoKMGRFH8OsXStX+c/h8+alvJybL9gZ5LJ3g0RNfzU2FR07aHOhn 5JKwWWDStldvE3tnl6JWNxKnE8eL4L4mfUYK+rv272pDeBdvFz+gGCl8Tugx5ibEKf BRapWrAAIY06iAEXuhDQxqOg3pjZEqaGpAhktIztRi4oTi5yJFkWuYFMEg5V5WLDJ4 ZTTxkmuswMhGA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Zhang Qiao , Roman Kagan , Peter Zijlstra , Sasha Levin , mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org Subject: [PATCH AUTOSEL 4.14 3/3] sched/fair: sanitize vruntime of entity being placed Date: Sat, 25 Feb 2023 22:44:30 -0500 Message-Id: <20230226034430.776472-3-sashal@kernel.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230226034430.776472-1-sashal@kernel.org> References: <20230226034430.776472-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Zhang Qiao [ Upstream commit 829c1651e9c4a6f78398d3e67651cef9bb6b42cc ] When a scheduling entity is placed onto cfs_rq, its vruntime is pulled to the base level (around cfs_rq->min_vruntime), so that the entity doesn't gain extra boost when placed backwards. However, if the entity being placed wasn't executed for a long time, its vruntime may get too far behind (e.g. while cfs_rq was executing a low-weight hog), which can inverse the vruntime comparison due to s64 overflow. This results in the entity being placed with its original vruntime way forwards, so that it will effectively never get to the cpu. To prevent that, ignore the vruntime of the entity being placed if it didn't execute for much longer than the characteristic sheduler time scale. [rkagan: formatted, adjusted commit log, comments, cutoff value] Signed-off-by: Zhang Qiao Co-developed-by: Roman Kagan Signed-off-by: Roman Kagan Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20230130122216.3555094-1-rkagan@amazon.de Signed-off-by: Sasha Levin --- kernel/sched/fair.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3ff60230710c9..afa21e43477fa 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3615,6 +3615,7 @@ static void place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) { u64 vruntime = cfs_rq->min_vruntime; + u64 sleep_time; /* * The 'current' period is already promised to the current tasks, @@ -3639,8 +3640,18 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) vruntime -= thresh; } - /* ensure we never gain time by being placed backwards. */ - se->vruntime = max_vruntime(se->vruntime, vruntime); + /* + * Pull vruntime of the entity being placed to the base level of + * cfs_rq, to prevent boosting it if placed backwards. If the entity + * slept for a long time, don't even try to compare its vruntime with + * the base as it may be too far off and the comparison may get + * inversed due to s64 overflow. + */ + sleep_time = rq_clock_task(rq_of(cfs_rq)) - se->exec_start; + if ((s64)sleep_time > 60LL * NSEC_PER_SEC) + se->vruntime = vruntime; + else + se->vruntime = max_vruntime(se->vruntime, vruntime); } static void check_enqueue_throttle(struct cfs_rq *cfs_rq); -- 2.39.0