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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02360C433EF for ; Tue, 5 Oct 2021 08:49:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DC35C6136F for ; Tue, 5 Oct 2021 08:49:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233357AbhJEIvh (ORCPT ); Tue, 5 Oct 2021 04:51:37 -0400 Received: from first.geanix.com ([116.203.34.67]:37336 "EHLO first.geanix.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233376AbhJEIvc (ORCPT ); Tue, 5 Oct 2021 04:51:32 -0400 Received: from skn-laptop (_gateway [172.25.0.1]) by first.geanix.com (Postfix) with ESMTPSA id 7570EC24F2; Tue, 5 Oct 2021 08:49:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=geanix.com; s=first; t=1633423779; bh=AUnXTubOTobfFxzBcRJ9H6QzFIiTxSYi3vnBtn38bE4=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=ca4ypouvW1ZLkNzvJktUrFio8Kx3ez/L0TDZ04MxVnDZWsLpZps1HPPgy92L88FD3 DOE+KYItMLf/YMYSsIKOsH6R3nAWf+dKcp60WubGprP6x3zGMiwxUPmqs8f+QYE2QP IOi9tSbHpqTHBm7zeiRbnZsE9VHEwCA0edl5jLc2v9NzXpd+U4f86DBtuVoh2fd1IB 8BaXbDg8F2chpFewkSHSWA2Gk78MQNh8kDaZ9uvZwPbxWScL/EH6DMGHqaoNJYHZSX RDMFRTti1Fp7WVOUcEu6Safg+xRcPCOS66HlhBc4ZIblKCvWSTJm10iyteW4B3kl2g PkOX+oxqbq+Kw== Date: Tue, 5 Oct 2021 10:49:38 +0200 From: Sean Nyekjaer To: Boris Brezillon Cc: Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Boris Brezillon , linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] mtd: rawnand: use mutex to protect access while in suspend Message-ID: <20211005084938.jcbw24umhehoiirs@skn-laptop> References: <20211004065608.3190348-1-sean@geanix.com> <20211004104147.579f3b01@collabora.com> <20211004085509.iikxtdvxpt6bri5c@skn-laptop> <20211004115817.18739936@collabora.com> <20211004101246.kagtezizympxupat@skn-laptop> <20211004134700.26327f6f@collabora.com> <20211005070930.epgxb5qzumk4awxq@skn-laptop> <20211005102300.5da6d480@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20211005102300.5da6d480@collabora.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 05, 2021 at 10:23:00AM +0200, Boris Brezillon wrote: > On Tue, 5 Oct 2021 09:09:30 +0200 > Sean Nyekjaer wrote: [ ... ] > > > > Have you seen the reproducer script? > > How would I know about this script or your previous attempt (mentioned > at the end of this email) given I was not Cc-ed on the previous > discussion, and nothing mentions it in this RFC... > That's why I shared it here ;) Initially I thought this was a bug introduced by exec_op. > > --- > > root@iwg26-v1:/data/root# cat /data/crash.sh > > #!/bin/sh -x > > > > echo enabled > /sys/devices/platform/soc/2100000.bus/21f4000.serial/tty/ttymxc4/power/wakeup > > > > rm /data/test50M > > dd if=/dev/urandom of=/tmp/test50M bs=1M count=50 > > cp /tmp/test50M /data/ & > > sleep 1 > > echo mem > /sys/power/state > > --- > > > > As seen in the log above disk is synced before suspend. > > cp is continuing to copy data to ubifs. > > And then user space processes are frozen. > > At this point the kernel thread would have unwritten data. > > > > We tried to solve this with: > > https://lkml.org/lkml/2021/9/1/280 > > I see. It's still unclear to me when the write happens. Is it in the > suspend path (before the system is actually suspended), or in the > resume path (when the system is being resumed). > > Anyway, let's admit writing to a storage device while it's suspended is > a valid use case and requires the storage layer to put this request on > old. This wait should not, IMHO, be handled at the NAND level, but at > the MTD level (using a waitqueue, and an atomic to make > suspended/resumed transitions safe). And abusing a mutex to implement > that is certainly not a good idea. I did't say this was the right solution ;) I actually asked in the RFC: "Should we introduce a new mutex? Or maybe a spin_lock?" What are you proposing, a waitqueue in mtd_info? That gets checked in mtd_write()/mtd_read()? /Sean 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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A4EEC433EF for ; Tue, 5 Oct 2021 08:50:26 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 684E36136F for ; Tue, 5 Oct 2021 08:50:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 684E36136F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=geanix.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=+Z6dlCQaC74mBJ9y6g7c6nlxUZu3V2/PSGnaX425tuQ=; b=He0u9dehyY+80O 3TrD7BjB1yboBAdTQfv2Wz14VTINbDDWmQCswBnhsyEi8NAQKLp58lt31ClkUNUI4t4T6mqmjJ9nY VWTQMC8TkxjYeCIXmxmKmpM9yMLaItqt6BE2V3DsIGWqaE/sn03M8y8PY47JZ16wdrv3ax7CFM8Mb +MlosfSBFU7M5h+OxoL1NulLVR6buh118Pbq8r826BAYim1p8Gn4xN6ZwEx7CECtJnDSD8r/bEbc8 aBvsrpScS3AlUjIvQQElt5oHISoWhxNC/SyiYlB+vlRKqoD0JHVEnvlqvcXfqDfGuJ7o9ifyrUo2t bXbNHKS5pMMI+HVqZJpQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mXg8x-009ZqI-Vw; Tue, 05 Oct 2021 08:49:48 +0000 Received: from first.geanix.com ([116.203.34.67]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mXg8t-009Zo9-Si for linux-mtd@lists.infradead.org; Tue, 05 Oct 2021 08:49:46 +0000 Received: from skn-laptop (_gateway [172.25.0.1]) by first.geanix.com (Postfix) with ESMTPSA id 7570EC24F2; Tue, 5 Oct 2021 08:49:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=geanix.com; s=first; t=1633423779; bh=AUnXTubOTobfFxzBcRJ9H6QzFIiTxSYi3vnBtn38bE4=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=ca4ypouvW1ZLkNzvJktUrFio8Kx3ez/L0TDZ04MxVnDZWsLpZps1HPPgy92L88FD3 DOE+KYItMLf/YMYSsIKOsH6R3nAWf+dKcp60WubGprP6x3zGMiwxUPmqs8f+QYE2QP IOi9tSbHpqTHBm7zeiRbnZsE9VHEwCA0edl5jLc2v9NzXpd+U4f86DBtuVoh2fd1IB 8BaXbDg8F2chpFewkSHSWA2Gk78MQNh8kDaZ9uvZwPbxWScL/EH6DMGHqaoNJYHZSX RDMFRTti1Fp7WVOUcEu6Safg+xRcPCOS66HlhBc4ZIblKCvWSTJm10iyteW4B3kl2g PkOX+oxqbq+Kw== Date: Tue, 5 Oct 2021 10:49:38 +0200 From: Sean Nyekjaer To: Boris Brezillon Cc: Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Boris Brezillon , linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] mtd: rawnand: use mutex to protect access while in suspend Message-ID: <20211005084938.jcbw24umhehoiirs@skn-laptop> References: <20211004065608.3190348-1-sean@geanix.com> <20211004104147.579f3b01@collabora.com> <20211004085509.iikxtdvxpt6bri5c@skn-laptop> <20211004115817.18739936@collabora.com> <20211004101246.kagtezizympxupat@skn-laptop> <20211004134700.26327f6f@collabora.com> <20211005070930.epgxb5qzumk4awxq@skn-laptop> <20211005102300.5da6d480@collabora.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211005102300.5da6d480@collabora.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211005_014944_103460_EE2518F4 X-CRM114-Status: GOOD ( 24.77 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org On Tue, Oct 05, 2021 at 10:23:00AM +0200, Boris Brezillon wrote: > On Tue, 5 Oct 2021 09:09:30 +0200 > Sean Nyekjaer wrote: [ ... ] > > > > Have you seen the reproducer script? > > How would I know about this script or your previous attempt (mentioned > at the end of this email) given I was not Cc-ed on the previous > discussion, and nothing mentions it in this RFC... > That's why I shared it here ;) Initially I thought this was a bug introduced by exec_op. > > --- > > root@iwg26-v1:/data/root# cat /data/crash.sh > > #!/bin/sh -x > > > > echo enabled > /sys/devices/platform/soc/2100000.bus/21f4000.serial/tty/ttymxc4/power/wakeup > > > > rm /data/test50M > > dd if=/dev/urandom of=/tmp/test50M bs=1M count=50 > > cp /tmp/test50M /data/ & > > sleep 1 > > echo mem > /sys/power/state > > --- > > > > As seen in the log above disk is synced before suspend. > > cp is continuing to copy data to ubifs. > > And then user space processes are frozen. > > At this point the kernel thread would have unwritten data. > > > > We tried to solve this with: > > https://lkml.org/lkml/2021/9/1/280 > > I see. It's still unclear to me when the write happens. Is it in the > suspend path (before the system is actually suspended), or in the > resume path (when the system is being resumed). > > Anyway, let's admit writing to a storage device while it's suspended is > a valid use case and requires the storage layer to put this request on > old. This wait should not, IMHO, be handled at the NAND level, but at > the MTD level (using a waitqueue, and an atomic to make > suspended/resumed transitions safe). And abusing a mutex to implement > that is certainly not a good idea. I did't say this was the right solution ;) I actually asked in the RFC: "Should we introduce a new mutex? Or maybe a spin_lock?" What are you proposing, a waitqueue in mtd_info? That gets checked in mtd_write()/mtd_read()? /Sean ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/