From patchwork Tue Sep 1 15:10:20 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 264451 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=unavailable 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 F0C94C433E2 for ; Tue, 1 Sep 2020 17:12:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C480B206FA for ; Tue, 1 Sep 2020 17:12:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598980379; bh=p8BE7X+nZ6st4U/GVQwBf0Sc/g1a6v51AjLXWy+aJXQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=OixIEH3jhhefrbFJtp6M4bP88yLC/gmCc+w/oy96JI2iizKDv7x1jbYA7OrjFLAXH u22BTCbwe6CQIhzsTbOEetDFJRg3myGsrLKq4Pk4k4Ix21d7VYbUxYBeQUq6Hj+3w6 7StK8c06XfW5I3Fdw73uACexBZstCXObu4FDRYek= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729230AbgIARMl (ORCPT ); Tue, 1 Sep 2020 13:12:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:60364 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729148AbgIAPPt (ORCPT ); Tue, 1 Sep 2020 11:15:49 -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 01A7F20767; Tue, 1 Sep 2020 15:15:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598973349; bh=p8BE7X+nZ6st4U/GVQwBf0Sc/g1a6v51AjLXWy+aJXQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OEZqYXW8UbF4cn/VEbjD3crpCh5iDN568k850oFxgxtMlQtpzGN3A8qxFV49uhuiv biQfk7hGIu/GaYpX3hHZL7G0TnWv4iESTZ7peRKrzy/hzYQstinnmBvblEs+5UJryy oJFlCk62meAFk9vYkVBesrT4EDKPvIdAqdSb54G4= 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 4.9 44/78] s390/cio: add cond_resched() in the slow_eval_known_fn() loop Date: Tue, 1 Sep 2020 17:10:20 +0200 Message-Id: <20200901150926.958300203@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200901150924.680106554@linuxfoundation.org> References: <20200901150924.680106554@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 39a2b0cde9e42..d81fdcd6a1fe0 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; }