From patchwork Tue Sep 1 15:10:23 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 310522 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 808F9C433E6 for ; Tue, 1 Sep 2020 15:25:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 539312078B for ; Tue, 1 Sep 2020 15:25:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598973920; bh=9WsD+M7msmhvOrmHNhbANDUr/qQT8t+aOQRv8aa9ybg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=MK0/YtO1hz4gfdCVwzJ3t7N/rIX5v3viLfd6Zey7JA90uyrT/adnG11Q+1ZZC6DQr jY/ti7Xut7gr+BUUcH7EmI/LngzCsrQmZNhTPCZXOldEbSxyXNFTPBHxfCuhUjsoyx yz9Khv1KQB05sHfYsmth8MoM6uBWqgpr5khhWZR4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730027AbgIAPZT (ORCPT ); Tue, 1 Sep 2020 11:25:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:49668 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729446AbgIAPZR (ORCPT ); Tue, 1 Sep 2020 11:25:17 -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 C3FB920FC3; Tue, 1 Sep 2020 15:25:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598973917; bh=9WsD+M7msmhvOrmHNhbANDUr/qQT8t+aOQRv8aa9ybg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xOmRR5UtgPqNWZJ/+y/PLwlB5uBHwxX48in7LPS812NbnbR+USiITowsJ5UaCBA19 qkJvYT3WI9hFLV5r40AfWYE8P+y8DK6ShneUJbv8FMzwwL1sY+8b6Vfm8T92w/+eXe WqBhb7QomJ71u1x1smChmQ1sGn7cfaFwFEnTWC1k= 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 4.19 068/125] s390/cio: add cond_resched() in the slow_eval_known_fn() loop Date: Tue, 1 Sep 2020 17:10:23 +0200 Message-Id: <20200901150937.911488032@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200901150934.576210879@linuxfoundation.org> References: <20200901150934.576210879@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 df09ed53ab459..825a8f2703b4f 100644 --- a/drivers/s390/cio/css.c +++ b/drivers/s390/cio/css.c @@ -615,6 +615,11 @@ 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; }