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=-9.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,T_DKIMWL_WL_HIGH,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 65A2EC072B1 for ; Thu, 30 May 2019 03:48:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3683A24D32 for ; Thu, 30 May 2019 03:48:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559188126; bh=qpIVF3Cx9pKmLiimFB7271ld1ODQuXJahy+4CSBYWh0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=u4oWhUbiJNSSdVCcDrx5jXGRnSkqPfixV3J949QXzkm4eLZ8dBa3+xyFmqaLe/tm1 2AvvSD0C+xxbDiOrlbw0edM5yweSa9+Vexyjwrn5NSXXBoJYMJxgD5DQCaReM98ZJ2 uPrNg83lwwP6qAyyv7DOzrM59K8je8ta6Fz+pLLs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732784AbfE3Dsp (ORCPT ); Wed, 29 May 2019 23:48:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:58016 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732147AbfE3DUS (ORCPT ); Wed, 29 May 2019 23:20:18 -0400 Received: from localhost (ip67-88-213-2.z213-88-67.customer.algx.net [67.88.213.2]) (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 9C3362490A; Thu, 30 May 2019 03:20:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559186417; bh=qpIVF3Cx9pKmLiimFB7271ld1ODQuXJahy+4CSBYWh0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Tp8a7dRkQRCgUE4oTArpY0OX4pLoaFNbsk4KqiVXExl4n9U+feELHrLWRzi1yIQVJ AnNFPtmC32cXsdhdrrGyUXl3TnT9xsyyJeycqaH31lhxTan4NMgUNMvL7+qzGlstu6 MQ6UegWZp5jrFGhSKQAvVZALl4WhMIKFf+7QPZgw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Farman , Farhan Ali , Halil Pasic , Cornelia Huck , Sasha Levin Subject: [PATCH 4.14 192/193] vfio-ccw: Prevent quiesce function going into an infinite loop Date: Wed, 29 May 2019 20:07:26 -0700 Message-Id: <20190530030513.378820673@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190530030446.953835040@linuxfoundation.org> References: <20190530030446.953835040@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ Upstream commit d1ffa760d22aa1d8190478e5ef555c59a771db27 ] The quiesce function calls cio_cancel_halt_clear() and if we get an -EBUSY we go into a loop where we: - wait for any interrupts - flush all I/O in the workqueue - retry cio_cancel_halt_clear During the period where we are waiting for interrupts or flushing all I/O, the channel subsystem could have completed a halt/clear action and turned off the corresponding activity control bits in the subchannel status word. This means the next time we call cio_cancel_halt_clear(), we will again start by calling cancel subchannel and so we can be stuck between calling cancel and halt forever. Rather than calling cio_cancel_halt_clear() immediately after waiting, let's try to disable the subchannel. If we succeed in disabling the subchannel then we know nothing else can happen with the device. Suggested-by: Eric Farman Signed-off-by: Farhan Ali Message-Id: <4d5a4b98ab1b41ac6131b5c36de18b76c5d66898.1555449329.git.alifm@linux.ibm.com> Reviewed-by: Eric Farman Acked-by: Halil Pasic Signed-off-by: Cornelia Huck Signed-off-by: Sasha Levin --- drivers/s390/cio/vfio_ccw_drv.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-) diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c index 59eb5e6d9c79d..6cd41086f23e4 100644 --- a/drivers/s390/cio/vfio_ccw_drv.c +++ b/drivers/s390/cio/vfio_ccw_drv.c @@ -38,26 +38,30 @@ int vfio_ccw_sch_quiesce(struct subchannel *sch) if (ret != -EBUSY) goto out_unlock; + iretry = 255; do { - iretry = 255; ret = cio_cancel_halt_clear(sch, &iretry); - while (ret == -EBUSY) { - /* - * Flush all I/O and wait for - * cancel/halt/clear completion. - */ - private->completion = &completion; - spin_unlock_irq(sch->lock); - wait_for_completion_timeout(&completion, 3*HZ); + if (ret == -EIO) { + pr_err("vfio_ccw: could not quiesce subchannel 0.%x.%04x!\n", + sch->schid.ssid, sch->schid.sch_no); + break; + } + + /* + * Flush all I/O and wait for + * cancel/halt/clear completion. + */ + private->completion = &completion; + spin_unlock_irq(sch->lock); - private->completion = NULL; - flush_workqueue(vfio_ccw_work_q); - spin_lock_irq(sch->lock); - ret = cio_cancel_halt_clear(sch, &iretry); - }; + if (ret == -EBUSY) + wait_for_completion_timeout(&completion, 3*HZ); + private->completion = NULL; + flush_workqueue(vfio_ccw_work_q); + spin_lock_irq(sch->lock); ret = cio_disable_subchannel(sch); } while (ret == -EBUSY); out_unlock: -- 2.20.1