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 9B7A3C433F5 for ; Fri, 8 Oct 2021 10:04:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8224760F5A for ; Fri, 8 Oct 2021 10:04:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239585AbhJHKG2 (ORCPT ); Fri, 8 Oct 2021 06:06:28 -0400 Received: from first.geanix.com ([116.203.34.67]:37346 "EHLO first.geanix.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239040AbhJHKGZ (ORCPT ); Fri, 8 Oct 2021 06:06:25 -0400 Received: from skn-laptop (_gateway [172.25.0.1]) by first.geanix.com (Postfix) with ESMTPSA id CFB13C3B02; Fri, 8 Oct 2021 10:04:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=geanix.com; s=first; t=1633687467; bh=t790EvsXc4ZoZ8yOdtaYuNWz3V452fkzKiJzSLy8OPQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=MK/kBQmKD5UuS+JEqqB8wJT+zDf5JDNfPkysg6ZTi3WIH1zfchoAHZnjc3/euVdyL x8EbPu4tsc98+6HOG6eD+BrD+D/8H/Pl250UofhpHZJYnEB/UWbTJ/TDjBjsdubrgd 2KtDPUDUq6ZlEd+HotNU5hX7x7zN2L92TcfT51yMzVGCHD3kmHgnz1JKZfLJevfvU4 7clsycAUcBMM/eOTIaakYW4yC5LB50mnvrdqIS88Z9YtgmICCx+pQz5oHl+IUTusyc 8QCbKAGJxKlXb5fzoyVryjWFFOEGkyGwmoYmhxVmaEvRV040WYsoU5VvQpnvp/X5qk MKHvg4oiu4TLQ== Date: Fri, 8 Oct 2021 12:04:25 +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: <20211008100425.uudzlda2n5ojqjzc@skn-laptop> References: <20211004101246.kagtezizympxupat@skn-laptop> <20211004134700.26327f6f@collabora.com> <20211005070930.epgxb5qzumk4awxq@skn-laptop> <20211005102300.5da6d480@collabora.com> <20211005084938.jcbw24umhehoiirs@skn-laptop> <20211005105836.6c300f25@collabora.com> <20211007114351.3nafhtpefezxhanc@skn-laptop> <20211007141858.314533f2@collabora.com> <20211007123916.w4oaooxfbawe6yw3@skn-laptop> <20211007151426.54db0764@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20211007151426.54db0764@collabora.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 07, 2021 at 03:14:26PM +0200, Boris Brezillon wrote: > On Thu, 7 Oct 2021 14:39:16 +0200 > Sean Nyekjaer wrote: > > > > > > > wait_queue doesn't really describe what this waitqueue is used for > > > (maybe resume_wq), and the suspended state should be here as well > > > (actually, there's one already). > > > > I'll rename to something meaningful. > > > > > > Actually, what we need is a way to prevent the device from being > > > suspended while accesses are still in progress, and new accesses from > > > being queued if a suspend is pending. So, I think you need a readwrite > > > lock here: > > > > > > * take the lock in read mode for all IO accesses, check the > > > mtd->suspended value > > > - if true, release the lock, and wait (retry on wakeup) > > > - if false, just do the IO > > > > > > * take the lock in write mode when you want to suspend/resume the > > > device and update the suspended field. Call wake_up_all() in the > > > resume path > > > > Could we use the chip->lock mutex for this? It's does kinda what you > > described above? > > No you can't. Remember I suggested to move all of that logic to > mtdcore.c, which doesn't know about the nand_chip struct. > > > If we introduce a new lock, do we really need to have the suspended as > > an atomic? > > Nope, I thought we could do without a lock, but we actually need to > track active IO requests, not just the suspended state. I have only added wait_queue to read and write operations. I'll have a look into where we should add further checks. > > > > > I will test with some wait and retry added to nand_get_device(). > > Again, I think there's a misunderstanding here: if you move it to the > mtd layer, it can't be done in nand_get_device(). But once you've > implemented it in mtdcore.c, you should be able to get rid of the > nand_chip->suspended field. I have moved the suspended atomic and wake_queue to mtdcore.c. And kept the suspended variable in nand_base as is fine for chip level suspend status. diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c index c8fd7f758938..6492071eb4da 100644 --- a/drivers/mtd/mtdcore.c +++ b/drivers/mtd/mtdcore.c @@ -42,15 +42,24 @@ static int mtd_cls_suspend(struct device *dev) { struct mtd_info *mtd = dev_get_drvdata(dev); - return mtd ? mtd_suspend(mtd) : 0; + if (mtd) { + atomic_inc(&mtd->suspended); + return mtd_suspend(mtd); + } + + return 0; } static int mtd_cls_resume(struct device *dev) { struct mtd_info *mtd = dev_get_drvdata(dev); - if (mtd) + if (mtd) { mtd_resume(mtd); + atomic_dec(&mtd->suspended); + wake_up_all(&mtd->resume_wq); + } + return 0; } @@ -678,6 +687,10 @@ int add_mtd_device(struct mtd_info *mtd) if (error) goto fail_nvmem_add; + init_waitqueue_head(&mtd->resume_wq); + + atomic_set(&mtd->suspended, 0); + mtd_debugfs_populate(mtd); device_create(&mtd_class, mtd->dev.parent, MTD_DEVT(i) + 1, NULL, @@ -1558,6 +1571,8 @@ int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops) struct mtd_ecc_stats old_stats = master->ecc_stats; int ret_code; + wait_event(mtd->resume_wq, atomic_read(&mtd->suspended) == 0); + ops->retlen = ops->oobretlen = 0; ret_code = mtd_check_oob_ops(mtd, from, ops); @@ -1597,6 +1612,8 @@ int mtd_write_oob(struct mtd_info *mtd, loff_t to, struct mtd_info *master = mtd_get_master(mtd); int ret; + wait_event(mtd->resume_wq, atomic_read(&mtd->suspended) == 0); + ops->retlen = ops->oobretlen = 0; if (!(mtd->flags & MTD_WRITEABLE)) diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h index 88227044fc86..70ede36092a9 100644 --- a/include/linux/mtd/mtd.h +++ b/include/linux/mtd/mtd.h @@ -360,6 +360,9 @@ struct mtd_info { int (*_get_device) (struct mtd_info *mtd); void (*_put_device) (struct mtd_info *mtd); + atomic_t suspended; + wait_queue_head_t resume_wq; + /* * flag indicates a panic write, low level drivers can take appropriate * action if required to ensure writes go through 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 19FB1C433F5 for ; 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h=Date:From:To:Cc:Subject:References:In-Reply-To; b=MK/kBQmKD5UuS+JEqqB8wJT+zDf5JDNfPkysg6ZTi3WIH1zfchoAHZnjc3/euVdyL x8EbPu4tsc98+6HOG6eD+BrD+D/8H/Pl250UofhpHZJYnEB/UWbTJ/TDjBjsdubrgd 2KtDPUDUq6ZlEd+HotNU5hX7x7zN2L92TcfT51yMzVGCHD3kmHgnz1JKZfLJevfvU4 7clsycAUcBMM/eOTIaakYW4yC5LB50mnvrdqIS88Z9YtgmICCx+pQz5oHl+IUTusyc 8QCbKAGJxKlXb5fzoyVryjWFFOEGkyGwmoYmhxVmaEvRV040WYsoU5VvQpnvp/X5qk MKHvg4oiu4TLQ== Date: Fri, 8 Oct 2021 12:04:25 +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: <20211008100425.uudzlda2n5ojqjzc@skn-laptop> References: <20211004101246.kagtezizympxupat@skn-laptop> <20211004134700.26327f6f@collabora.com> <20211005070930.epgxb5qzumk4awxq@skn-laptop> <20211005102300.5da6d480@collabora.com> <20211005084938.jcbw24umhehoiirs@skn-laptop> <20211005105836.6c300f25@collabora.com> <20211007114351.3nafhtpefezxhanc@skn-laptop> <20211007141858.314533f2@collabora.com> <20211007123916.w4oaooxfbawe6yw3@skn-laptop> <20211007151426.54db0764@collabora.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211007151426.54db0764@collabora.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211008_030432_947414_6BE330A0 X-CRM114-Status: GOOD ( 36.47 ) 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 Thu, Oct 07, 2021 at 03:14:26PM +0200, Boris Brezillon wrote: > On Thu, 7 Oct 2021 14:39:16 +0200 > Sean Nyekjaer wrote: > > > > > > > wait_queue doesn't really describe what this waitqueue is used for > > > (maybe resume_wq), and the suspended state should be here as well > > > (actually, there's one already). > > > > I'll rename to something meaningful. > > > > > > Actually, what we need is a way to prevent the device from being > > > suspended while accesses are still in progress, and new accesses from > > > being queued if a suspend is pending. So, I think you need a readwrite > > > lock here: > > > > > > * take the lock in read mode for all IO accesses, check the > > > mtd->suspended value > > > - if true, release the lock, and wait (retry on wakeup) > > > - if false, just do the IO > > > > > > * take the lock in write mode when you want to suspend/resume the > > > device and update the suspended field. Call wake_up_all() in the > > > resume path > > > > Could we use the chip->lock mutex for this? It's does kinda what you > > described above? > > No you can't. Remember I suggested to move all of that logic to > mtdcore.c, which doesn't know about the nand_chip struct. > > > If we introduce a new lock, do we really need to have the suspended as > > an atomic? > > Nope, I thought we could do without a lock, but we actually need to > track active IO requests, not just the suspended state. I have only added wait_queue to read and write operations. I'll have a look into where we should add further checks. > > > > > I will test with some wait and retry added to nand_get_device(). > > Again, I think there's a misunderstanding here: if you move it to the > mtd layer, it can't be done in nand_get_device(). But once you've > implemented it in mtdcore.c, you should be able to get rid of the > nand_chip->suspended field. I have moved the suspended atomic and wake_queue to mtdcore.c. And kept the suspended variable in nand_base as is fine for chip level suspend status. diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c index c8fd7f758938..6492071eb4da 100644 --- a/drivers/mtd/mtdcore.c +++ b/drivers/mtd/mtdcore.c @@ -42,15 +42,24 @@ static int mtd_cls_suspend(struct device *dev) { struct mtd_info *mtd = dev_get_drvdata(dev); - return mtd ? mtd_suspend(mtd) : 0; + if (mtd) { + atomic_inc(&mtd->suspended); + return mtd_suspend(mtd); + } + + return 0; } static int mtd_cls_resume(struct device *dev) { struct mtd_info *mtd = dev_get_drvdata(dev); - if (mtd) + if (mtd) { mtd_resume(mtd); + atomic_dec(&mtd->suspended); + wake_up_all(&mtd->resume_wq); + } + return 0; } @@ -678,6 +687,10 @@ int add_mtd_device(struct mtd_info *mtd) if (error) goto fail_nvmem_add; + init_waitqueue_head(&mtd->resume_wq); + + atomic_set(&mtd->suspended, 0); + mtd_debugfs_populate(mtd); device_create(&mtd_class, mtd->dev.parent, MTD_DEVT(i) + 1, NULL, @@ -1558,6 +1571,8 @@ int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops) struct mtd_ecc_stats old_stats = master->ecc_stats; int ret_code; + wait_event(mtd->resume_wq, atomic_read(&mtd->suspended) == 0); + ops->retlen = ops->oobretlen = 0; ret_code = mtd_check_oob_ops(mtd, from, ops); @@ -1597,6 +1612,8 @@ int mtd_write_oob(struct mtd_info *mtd, loff_t to, struct mtd_info *master = mtd_get_master(mtd); int ret; + wait_event(mtd->resume_wq, atomic_read(&mtd->suspended) == 0); + ops->retlen = ops->oobretlen = 0; if (!(mtd->flags & MTD_WRITEABLE)) diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h index 88227044fc86..70ede36092a9 100644 --- a/include/linux/mtd/mtd.h +++ b/include/linux/mtd/mtd.h @@ -360,6 +360,9 @@ struct mtd_info { int (*_get_device) (struct mtd_info *mtd); void (*_put_device) (struct mtd_info *mtd); + atomic_t suspended; + wait_queue_head_t resume_wq; + /* * flag indicates a panic write, low level drivers can take appropriate * action if required to ensure writes go through ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/