From patchwork Tue Sep 1 15:10:26 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 264477 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=-13.0 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, 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 16089C43461 for ; Tue, 1 Sep 2020 17:05:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D0DB021527 for ; Tue, 1 Sep 2020 17:05:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598979931; bh=4TG4KMIY0v5Q13GLnA/64q9bgsmokJekESKQfdHsjfM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=PzESr6tkVWlLJn52bc/HVIukJYAiV1/h14//9q2LDT6H+a15iXNrLDAoFkz1d3eEG Wa9gWBdYeIe0+eY1dylPe26EKirz312bQCYBYBFWTVL+bCWRpCzhHYcT3uxlGm6HJL Vz0k8bXDs8oG/U90APB+4RANtAenZfx9ShTTrBsc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728872AbgIARFa (ORCPT ); Tue, 1 Sep 2020 13:05:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:38864 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729523AbgIAPTj (ORCPT ); Tue, 1 Sep 2020 11:19:39 -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 E04E421582; Tue, 1 Sep 2020 15:19:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598973572; bh=4TG4KMIY0v5Q13GLnA/64q9bgsmokJekESKQfdHsjfM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Smck+Qkj7DDRIIBr9DSsKXUtWMyCRRmQti9sjPg2cKKydTc/NMcMUVdhVS5TMftpW /a9WwyvxxJ/d9liEwEjn6x46aFr9xx0+2gE/mLAkqA/1/Uh6SaZlm64Fo6rytYTYnM 92yjGTFqCJDHw4lE28uApS54vRMynRTphEDOhEhc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Peter Oberparleiter , Vineeth Vijayan , Heiko Carstens , Sasha Levin Subject: [PATCH 4.14 52/91] s390/cio: add cond_resched() in the slow_eval_known_fn() loop Date: Tue, 1 Sep 2020 17:10:26 +0200 Message-Id: <20200901150930.715715759@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200901150928.096174795@linuxfoundation.org> References: <20200901150928.096174795@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Vineeth Vijayan [ Upstream commit 0b8eb2ee9da1e8c9b8082f404f3948aa82a057b2 ] The scanning through subchannels during the time of an event could take significant amount of time in case of platforms with lots of known subchannels. This might result in higher scheduling latencies for other tasks especially on systems with a single CPU. Add cond_resched() call, as the loop in slow_eval_known_fn() can be executed for a longer duration. Reviewed-by: Peter Oberparleiter Signed-off-by: Vineeth Vijayan Signed-off-by: Heiko Carstens Signed-off-by: Sasha Levin --- drivers/s390/cio/css.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c index dadff1838fec1..e2026d54dd375 100644 --- a/drivers/s390/cio/css.c +++ b/drivers/s390/cio/css.c @@ -581,6 +581,11 @@ static int slow_eval_known_fn(struct subchannel *sch, void *data) rc = css_evaluate_known_subchannel(sch, 1); if (rc == -EAGAIN) css_schedule_eval(sch->schid); + /* + * The loop might take long time for platforms with lots of + * known devices. Allow scheduling here. + */ + cond_resched(); } return 0; }