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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 C661DC432C3 for ; Mon, 18 Nov 2019 17:49:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9318E21D7A for ; Mon, 18 Nov 2019 17:49:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726427AbfKRRtS (ORCPT ); Mon, 18 Nov 2019 12:49:18 -0500 Received: from mail-pf1-f194.google.com ([209.85.210.194]:42410 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726314AbfKRRtR (ORCPT ); Mon, 18 Nov 2019 12:49:17 -0500 Received: by mail-pf1-f194.google.com with SMTP id s5so10721522pfh.9 for ; Mon, 18 Nov 2019 09:49:17 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=+MkRqVTvzRw3994vsh9VAMDm8kV9advJ/c8aIWpeCW4=; b=jWyXCnWTh0p0KvgMtC5En0yBNo/nwViS1B6PSuc+qfuiPVb5QS9G2JxQea4w7DllG4 BLGsRzzfMoyR4PyLbS8hTXx/OT2U7a23bgHeQiqGmpBX2EDtDhublA2IFaqI//Nohf/Y 0TTqyQBM3rDzvQHp8CwVHeJ2CPwdAYuvP7hu7hVcl1HxUlrtdqq79Yguf2thL/+G+Lw0 WuLjTcBTC8YVK0t6GZyVWW1HrDZX3vB1CwFVnuYUxP3h+kCHjbiMcFumO6XUmyuQIWHE MwFB96mPjRRwd2dP/+59+X/Ywztwuw0/VsJK9JRyZGusEfAHeNXUqgsq9LvgWjiWMU9e o9bw== X-Gm-Message-State: APjAAAUx0vxQYNrByXef9dDqwMjozUmkzItEPC0B2MrfR+jpdVHb3/Us jgwNr2KzT3BAHJCPaeD/vyvqS2oS X-Google-Smtp-Source: APXvYqx7u6Z1u/jeJteNI+F4WfB9vGl0PSzjm86TxA/cO5MBMtSjHUDcP1qTWBbQ/7NQfbFEfQx9lQ== X-Received: by 2002:a63:d70e:: with SMTP id d14mr589366pgg.10.1574099356775; Mon, 18 Nov 2019 09:49:16 -0800 (PST) Received: from desktop-bart.svl.corp.google.com ([2620:15c:2cd:202:4308:52a3:24b6:2c60]) by smtp.gmail.com with ESMTPSA id w5sm23154166pfd.31.2019.11.18.09.49.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 18 Nov 2019 09:49:15 -0800 (PST) Subject: Re: [EXT] Re: [PATCH v5 4/4] ufs: Simplify the clock scaling mechanism implementation To: cang@codeaurora.org Cc: "Bean Huo (beanhuo)" , "Martin K . Petersen" , "James E . J . Bottomley" , Avri Altman , Asutosh Das , stummala@codeaurora.org, Vignesh Raghavendra , linux-scsi@vger.kernel.org, Stanley Chu , Tomas Winkler References: <20191112173743.141503-1-bvanassche@acm.org> <20191112173743.141503-5-bvanassche@acm.org> <8acd9237-7414-5dce-5285-69ed3ce6f28c@acm.org> <425c127b-d8f9-0a96-64c1-4c9862ca5f43@acm.org> <0101016e7ca0e791-30050d63-c260-4cc3-a12b-658b7aa70031-000000@us-west-2.amazonses.com> From: Bart Van Assche Message-ID: Date: Mon, 18 Nov 2019 09:49:14 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <0101016e7ca0e791-30050d63-c260-4cc3-a12b-658b7aa70031-000000@us-west-2.amazonses.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On 11/17/19 7:49 PM, cang@codeaurora.org wrote: > After this point, dev commands can be sent on hba->cmd_queue. > But there are multiple entries which users can send dev commands through in ufs-sysfs.c. > So the clock scaling sequence lost its protection from being disturbed. Hi Can, My understanding of the current implementation (Martin's 5.5/scsi-queue branch) is that hba->clk_scaling_lock serializes clock scaling and submission of SCSI and device commands but not the submission of TMFs. I think that the following call chain allows user space to submit TMFs while clock scaling is in progress: submit UPIU_TRANSACTION_TASK_REQ on an UFS BSG queue -> ufs_bsg_request() -> ufshcd_exec_raw_upiu_cmd(msgcode = UPIU_TRANSACTION_TASK_REQ) -> ufshcd_exec_raw_upiu_cmd() -> __ufshcd_issue_tm_cmd() Is that a feature or is that rather unintended behavior? Anyway, can you have a look at the patch below and verify whether it preserves existing behavior? Thank you, Bart. Subject: [PATCH] ufs: Simplify the clock scaling mechanism implementation Scaling the clock is only safe while no commands are in progress. The current clock scaling implementation uses hba->clk_scaling_lock to serialize clock scaling against the following three functions: * ufshcd_queuecommand() (uses sdev->request_queue) * ufshcd_exec_dev_cmd() (uses hba->cmd_queue) * ufshcd_issue_devman_upiu_cmd() (uses hba->cmd_queue) __ufshcd_issue_tm_cmd(), which uses hba->tmf_queue, is not serialized against clock scaling. Use blk_mq_{un,}freeze_queue() to block submission of new commands and to wait for ongoing commands to complete. This patch removes a semaphore down and up operation pair from the hot path. Cc: Bean Huo Cc: Avri Altman Cc: Stanley Chu Cc: Tomas Winkler Signed-off-by: Bart Van Assche --- drivers/scsi/ufs/ufshcd.c | 116 +++++++++++--------------------------- drivers/scsi/ufs/ufshcd.h | 1 - 2 files changed, 34 insertions(+), 83 deletions(-) diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 5314e8bfeeb6..46950cc87dc5 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -971,65 +971,6 @@ static bool ufshcd_is_devfreq_scaling_required(struct ufs_hba *hba, return false; } -static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba, - u64 wait_timeout_us) -{ - unsigned long flags; - int ret = 0; - u32 tm_doorbell; - u32 tr_doorbell; - bool timeout = false, do_last_check = false; - ktime_t start; - - ufshcd_hold(hba, false); - spin_lock_irqsave(hba->host->host_lock, flags); - /* - * Wait for all the outstanding tasks/transfer requests. - * Verify by checking the doorbell registers are clear. - */ - start = ktime_get(); - do { - if (hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL) { - ret = -EBUSY; - goto out; - } - - tm_doorbell = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL); - tr_doorbell = ufshcd_readl(hba, REG_UTP_TRANSFER_REQ_DOOR_BELL); - if (!tm_doorbell && !tr_doorbell) { - timeout = false; - break; - } else if (do_last_check) { - break; - } - - spin_unlock_irqrestore(hba->host->host_lock, flags); - schedule(); - if (ktime_to_us(ktime_sub(ktime_get(), start)) > - wait_timeout_us) { - timeout = true; - /* - * We might have scheduled out for long time so make - * sure to check if doorbells are cleared by this time - * or not. - */ - do_last_check = true; - } - spin_lock_irqsave(hba->host->host_lock, flags); - } while (tm_doorbell || tr_doorbell); - - if (timeout) { - dev_err(hba->dev, - "%s: timedout waiting for doorbell to clear (tm=0x%x, tr=0x%x)\n", - __func__, tm_doorbell, tr_doorbell); - ret = -EBUSY; - } -out: - spin_unlock_irqrestore(hba->host->host_lock, flags); - ufshcd_release(hba); - return ret; -} - /** * ufshcd_scale_gear - scale up/down UFS gear * @hba: per adapter instance @@ -1079,27 +1020,50 @@ static int ufshcd_scale_gear(struct ufs_hba *hba, bool scale_up) static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba) { - #define DOORBELL_CLR_TOUT_US (1000 * 1000) /* 1 sec */ - int ret = 0; + unsigned long deadline = jiffies + HZ; + struct scsi_device *sdev; + int res = 0; + /* * make sure that there are no outstanding requests when * clock scaling is in progress */ - ufshcd_scsi_block_requests(hba); - down_write(&hba->clk_scaling_lock); - if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) { - ret = -EBUSY; - up_write(&hba->clk_scaling_lock); - ufshcd_scsi_unblock_requests(hba); + shost_for_each_device(sdev, hba->host) + blk_freeze_queue_start(sdev->request_queue); + blk_freeze_queue_start(hba->cmd_queue); + blk_freeze_queue_start(hba->tmf_queue); + shost_for_each_device(sdev, hba->host) { + if (blk_mq_freeze_queue_wait_timeout(sdev->request_queue, + max_t(long, 0, deadline - jiffies)) <= 0) { + goto err; + } } + if (blk_mq_freeze_queue_wait_timeout(hba->cmd_queue, + max_t(long, 0, deadline - jiffies)) <= 0) + goto err; + if (blk_mq_freeze_queue_wait_timeout(hba->tmf_queue, + max_t(long, 0, deadline - jiffies)) <= 0) + goto err; - return ret; +out: + blk_mq_unfreeze_queue(hba->tmf_queue); + return res; + +err: + blk_mq_unfreeze_queue(hba->cmd_queue); + shost_for_each_device(sdev, hba->host) + blk_mq_unfreeze_queue(sdev->request_queue); + res = -ETIMEDOUT; + goto out; } static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba) { - up_write(&hba->clk_scaling_lock); - ufshcd_scsi_unblock_requests(hba); + struct scsi_device *sdev; + + blk_mq_unfreeze_queue(hba->cmd_queue); + shost_for_each_device(sdev, hba->host) + blk_mq_unfreeze_queue(sdev->request_queue); } /** @@ -2394,9 +2358,6 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd) BUG(); } - if (!down_read_trylock(&hba->clk_scaling_lock)) - return SCSI_MLQUEUE_HOST_BUSY; - spin_lock_irqsave(hba->host->host_lock, flags); switch (hba->ufshcd_state) { case UFSHCD_STATE_OPERATIONAL: @@ -2462,7 +2423,6 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd) out_unlock: spin_unlock_irqrestore(hba->host->host_lock, flags); out: - up_read(&hba->clk_scaling_lock); return err; } @@ -2616,8 +2576,6 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba, struct completion wait; unsigned long flags; - down_read(&hba->clk_scaling_lock); - /* * Get free slot, sleep if slots are unavailable. * Even though we use wait_event() which sleeps indefinitely, @@ -2653,7 +2611,6 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba, out_put_tag: blk_put_request(req); - up_read(&hba->clk_scaling_lock); return err; } @@ -5771,8 +5728,6 @@ static int ufshcd_issue_devman_upiu_cmd(struct ufs_hba *hba, unsigned long flags; u32 upiu_flags; - down_read(&hba->clk_scaling_lock); - req = blk_get_request(q, REQ_OP_DRV_OUT, 0); if (IS_ERR(req)) return PTR_ERR(req); @@ -5854,7 +5809,6 @@ static int ufshcd_issue_devman_upiu_cmd(struct ufs_hba *hba, } blk_put_request(req); - up_read(&hba->clk_scaling_lock); return err; } @@ -8323,8 +8277,6 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq) /* Initialize mutex for device management commands */ mutex_init(&hba->dev_cmd.lock); - init_rwsem(&hba->clk_scaling_lock); - ufshcd_init_clk_gating(hba); ufshcd_init_clk_scaling(hba); diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h index 5865e16f53a6..5ebb920ae874 100644 --- a/drivers/scsi/ufs/ufshcd.h +++ b/drivers/scsi/ufs/ufshcd.h @@ -724,7 +724,6 @@ struct ufs_hba { enum bkops_status urgent_bkops_lvl; bool is_urgent_bkops_lvl_checked; - struct rw_semaphore clk_scaling_lock; struct ufs_desc_size desc_size; atomic_t scsi_block_reqs_cnt;