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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 916D9C4338F for ; Thu, 19 Aug 2021 17:50:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 71F2D610CE for ; Thu, 19 Aug 2021 17:50:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233935AbhHSRv0 (ORCPT ); Thu, 19 Aug 2021 13:51:26 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:38752 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231196AbhHSRvS (ORCPT ); Thu, 19 Aug 2021 13:51:18 -0400 Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 3D6CA20111; Thu, 19 Aug 2021 17:50:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1629395441; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=KuvQiu5LKZQFu+8mD8swgYmQInz949y0M7/GFw+osLg=; b=dma+7MyN4z6DRiIxoB66+aFeXmgcdL0yYQO3X+JaKUQFZmEVI8HEDeOLtvzbwQ+0nlRz04 tbz6vxbV0Hq+3jZu+MIguZD9q46VbcxDT1kzozKC3HnO90ZMQ5cMw1GsUiz+1yQ+WAWzoy WfAAqUvmvlboFtlfqzLnuP3SrqzARNA= Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap1.suse-dmz.suse.de (Postfix) with ESMTPS id 1473213AB1; Thu, 19 Aug 2021 17:50:41 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap1.suse-dmz.suse.de with ESMTPSA id aGSJBPGZHmHnOQAAGKfGzw (envelope-from ); Thu, 19 Aug 2021 17:50:41 +0000 From: =?UTF-8?q?Michal=20Koutn=C3=BD?= To: linux-kernel@vger.kernel.org Cc: Vincent Guittot , Phil Auld , Ingo Molnar , Peter Zijlstra , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Odin Ugedal , Rik van Riel , Giovanni Gherdovich Subject: [RFC PATCH v2 1/5] sched/fair: Add ancestors of unthrottled undecayed cfs_rq Date: Thu, 19 Aug 2021 19:50:30 +0200 Message-Id: <20210819175034.4577-2-mkoutny@suse.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210819175034.4577-1-mkoutny@suse.com> References: <20210819175034.4577-1-mkoutny@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since commit a7b359fc6a37 ("sched/fair: Correctly insert cfs_rq's to list on unthrottle") we add cfs_rqs with no runnable tasks but not fully decayed into the load (leaf) list. We may ignore adding some ancestors and therefore breaking tmp_alone_branch invariant. This broke LTP test cfs_bandwidth01 and it was partially fixed in commit fdaba61ef8a2 ("sched/fair: Ensure that the CFS parent is added after unthrottling"). I noticed the named test still fails even with the fix (but with low probability, 1 in ~1000 executions of the test). The reason is when bailing out of unthrottle_cfs_rq early, we may miss adding ancestors of the unthrottled cfs_rq, thus, not joining tmp_alone_branch properly. Fix this by adding ancestors if we notice the unthrottled cfs_rq was added to the load list. Fixes: a7b359fc6a37 ("sched/fair: Correctly insert cfs_rq's to list on unthrottle") Signed-off-by: Michal Koutný --- kernel/sched/fair.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 44c452072a1b..2c41a9007928 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4898,8 +4898,16 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) /* update hierarchical throttle state */ walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq); - if (!cfs_rq->load.weight) + if (!cfs_rq->load.weight) { + /* Nothing to run but something to decay? Complete the branch */ + if (cfs_rq->on_list) + for_each_sched_entity(se) { + if (list_add_leaf_cfs_rq(group_cfs_rq(se))) + break; + } + assert_list_leaf_cfs_rq(rq); return; + } task_delta = cfs_rq->h_nr_running; idle_task_delta = cfs_rq->idle_h_nr_running; -- 2.32.0