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 8B7AAC7EE30 for ; Sun, 26 Feb 2023 03:46:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230143AbjBZDqk (ORCPT ); Sat, 25 Feb 2023 22:46:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55270 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229882AbjBZDqN (ORCPT ); Sat, 25 Feb 2023 22:46:13 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7386914987; Sat, 25 Feb 2023 19:45:42 -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 ams.source.kernel.org (Postfix) with ESMTPS id CA333B80B8D; Sun, 26 Feb 2023 03:44:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9FC6DC433D2; Sun, 26 Feb 2023 03:44:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1677383063; bh=FWzmx+O1miXysAo0ZEmcnjwGaVYR6P9i2QCNYCI7EZg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BkA1WVCQ6TuaVfTReGULgiUiVPLtDesrbhVY6NFFIdTsovl4ByD/68Iavz8BAU2GJ yu4+696/knOMZnS0sQdc6oBtoJQdSwKDpDL/K0qy2qCRz6i1p4hHe41f1+pO43etkp pukN8dgxUnJfqR9z5EQ7HCuEmoQTo0gJZQ0YEDgNU/1Sc1PfNwyQjRW1/b3dVrFD8O 2niHzPexs0WfmM4LGDPfPRuuNavVWycX2X4ACrqqCgmZptYCJmmTmkF+cZNX1mrJQt XQiVimeRbpOIFOiFV5B4t266S2iEtTSNMmehmHzfgMBgsNrZ+EvWC1Ob7nDZd2n8pS Ke31GcLmBITfQ== 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 5.4 4/4] sched/fair: sanitize vruntime of entity being placed Date: Sat, 25 Feb 2023 22:44:16 -0500 Message-Id: <20230226034417.775491-4-sashal@kernel.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230226034417.775491-1-sashal@kernel.org> References: <20230226034417.775491-1-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 d2a68ae7596ec..97ede6b914422 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3881,6 +3881,7 @@ 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, @@ -3905,8 +3906,18 @@ 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