From patchwork Tue Sep 1 15:10:19 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 264831 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 1EDBEC433E6 for ; Tue, 1 Sep 2020 15:13:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E271620BED for ; Tue, 1 Sep 2020 15:13:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598973183; bh=BWK2hS0GdXLTqvn3LCDebg7pXZphF7c3VLKfxq34sFk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Sx4tu/qEUk1lIuRwOPjlmISC8p0q5ho0P1VB7LdzmJ/d2tzZx3D/SKEyrQahDRuyf 13JYkNSHmBps2QMNVPArPJiBLwQAyuVvYxeby9UPmr9wyDn3eOKx23i6K+rZ5sQx2c 3WF9IlJ4Q5g5bvMQFE8ryLPMZs6i2dxgAYj/uPi4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728826AbgIAPMz (ORCPT ); Tue, 1 Sep 2020 11:12:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:55550 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728820AbgIAPMx (ORCPT ); Tue, 1 Sep 2020 11:12:53 -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 354D42078B; Tue, 1 Sep 2020 15:12:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598973172; bh=BWK2hS0GdXLTqvn3LCDebg7pXZphF7c3VLKfxq34sFk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zbZBpOFbvapX3/RF5Q+n2i6d4h8YGkxCuXQWDKWtP+xqRa1dQE2hh4xkg5KXCFXFL YWoPOJfahju9kLjR8OkAl73hn//8lm+iyUOQ6tWi1TjEz/rDV+BS2CDbPytsG3xUJw QiQxvLJtRJkXIUpES2r/h6LR4zIaikq8ahvhzFec= 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 4.4 36/62] s390/cio: add cond_resched() in the slow_eval_known_fn() loop Date: Tue, 1 Sep 2020 17:10:19 +0200 Message-Id: <20200901150922.532967816@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200901150920.697676718@linuxfoundation.org> References: <20200901150920.697676718@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 8ecc956ecb59c..370a3a2c6de73 100644 --- a/drivers/s390/cio/css.c +++ b/drivers/s390/cio/css.c @@ -529,6 +529,11 @@ 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; }