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 2D5D7C6FA8E for ; Sun, 26 Feb 2023 03:46:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229919AbjBZDq3 (ORCPT ); Sat, 25 Feb 2023 22:46:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54558 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229990AbjBZDqI (ORCPT ); Sat, 25 Feb 2023 22:46:08 -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 06E9718174; Sat, 25 Feb 2023 19:45:31 -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 ED7B760BE9; Sun, 26 Feb 2023 03:44:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5ED01C4339B; Sun, 26 Feb 2023 03:44:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1677383056; bh=cjwEOnzBjeN7oLDg7qAnbEAnbRdzHKHGwWDhPiqSgUg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BvU3hEhc1i2KkQAzYR8EsEyFsGA8K11UyOKCSBeINxcWQfLufr4+fOIT7SYQQ28AU IBxoIp8iZv8aXPcLRhpl1Gygqaqq2Abb97iPrkol6DKqqCD72O+xTn3zgRkyNwrPtF Iqd+181sWYyXPPPzSFdVYJ0OEEMDYcW18jwYKoBzHxzrOyuu3XKkztHOIvTloOvbZq Ps9SNvkZPRsZb7Y/gENl2mx9Q6b/VJRPqZ5hcSclfwQd0xkKAY7nyMcn8H0JACPx+j S5xuNooORbG4VZ8hH7P1yT+phwPrn0hH6JDlHCpmFCTjZ64vsVEH4S2/J9+AvDyZHc 74J4azTm7eI7A== 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 5.10 5/5] sched/fair: sanitize vruntime of entity being placed Date: Sat, 25 Feb 2023 22:44:08 -0500 Message-Id: <20230226034408.774670-5-sashal@kernel.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230226034408.774670-1-sashal@kernel.org> References: <20230226034408.774670-1-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: stable@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 c39d2fc3f9945..68166c599a355 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4278,6 +4278,7 @@ 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, @@ -4302,8 +4303,18 @@ 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