linux-kernel - Re: [PATCH v1 1/1] scsi: ufs: core: fix device management cmd timeout flow

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Date:   Fri, 2 Dec 2022 10:49:33 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     Mason Zhang <mason.zhang@...iatek.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E . J . Bottomley" <jejb@...ux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Bean Huo <beanhuo@...ron.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Jinyoung Choi <j-young.choi@...sung.com>
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Peter Wang <peter.wang@...iatek.com>,
        Peng Zhou <peng.zhou@...iatek.com>, wsd_upstream@...iatek.com
Subject: Re: [PATCH v1 1/1] scsi: ufs: core: fix device management cmd timeout
 flow

On 12/2/22 02:58, Mason Zhang wrote:
> From: Mason Zhang <Mason.Zhang@...iatek.com>
> 
> In ufs error handler flow, host will send device management cmd(NOP OUT)
> to device for recovery link. If cmd response timeout, and clear doorbell
> fail, ufshcd_wait_for_dev_cmd will do nothing and return,
> hba->dev_cmd.complete struct not set to null.
> 
> In this time, if cmd has been responsed by device, then it will
> call complete() in __ufshcd_transfer_req_compl, because of complete
> struct is alloced in stack, then the KE will occur.
> 
> Fix the following crash:
>    ipanic_die+0x24/0x38 [mrdump]
>    die+0x344/0x748
>    arm64_notify_die+0x44/0x104
>    do_debug_exception+0x104/0x1e0
>    el1_dbg+0x38/0x54
>    el1_sync_handler+0x40/0x88
>    el1_sync+0x8c/0x140
>    queued_spin_lock_slowpath+0x2e4/0x3c0
>    __ufshcd_transfer_req_compl+0x3b0/0x1164
>    ufshcd_trc_handler+0x15c/0x308
>    ufshcd_host_reset_and_restore+0x54/0x260
>    ufshcd_reset_and_restore+0x28c/0x57c
>    ufshcd_err_handler+0xeb8/0x1b6c
>    process_one_work+0x288/0x964
>    worker_thread+0x4bc/0xc7c
>    kthread+0x15c/0x264
>    ret_from_fork+0x10/0x30
> 
> Change-Id: Id17da259894294b61bef41cf7dfb94506e7e0310

Please verify patches with checkpatch before posting these upstream. Checkpatch
will tell you that Change-Id tags must be removed before posting a patch upstream.

> Signed-off-by: Mason Zhang <Mason.Zhang@...iatek.com>
> ---
>   drivers/ufs/core/ufshcd.c | 46 ++++++++++++++++++---------------------
>   1 file changed, 21 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index b1f59a5fe632..2b4934a562a6 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -2979,35 +2979,31 @@ static int ufshcd_wait_for_dev_cmd(struct ufs_hba *hba,
>   		err = -ETIMEDOUT;
>   		dev_dbg(hba->dev, "%s: dev_cmd request timedout, tag %d\n",
>   			__func__, lrbp->task_tag);
> -		if (ufshcd_clear_cmds(hba, 1U << lrbp->task_tag) == 0) {
> +		if (ufshcd_clear_cmds(hba, 1U << lrbp->task_tag) == 0)
>   			/* successfully cleared the command, retry if needed */
>   			err = -EAGAIN;
> +		/*
> +		 * Since clearing the command succeeded we also need to
> +		 * clear the task tag bit from the outstanding_reqs
> +		 * variable.
> +		 */
> +		spin_lock_irqsave(&hba->outstanding_lock, flags);
> +		pending = test_bit(lrbp->task_tag,
> +				   &hba->outstanding_reqs);
> +		if (pending) {
> +			hba->dev_cmd.complete = NULL;
> +			__clear_bit(lrbp->task_tag,
> +				    &hba->outstanding_reqs);
> +		}
> +		spin_unlock_irqrestore(&hba->outstanding_lock, flags);

I don't think it is safe to clear the corresponding bit from outstanding_reqs
if ufshcd_clear_cmds() returns a value != 0.

Instead of making all these changes, would the following patch be sufficient?

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index bb4cbfe7fd57..d5deec621d2a 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -3008,6 +3008,9 @@ static int ufshcd_wait_for_dev_cmd(struct ufs_hba *hba,
  		} else {
  			dev_err(hba->dev, "%s: failed to clear tag %d\n",
  				__func__, lrbp->task_tag);
+			spin_lock_irqsave(&hba->outstanding_lock, flags);
+			hba->dev_cmd.complete = NULL;
+			spin_unlock_irqrestore(&hba->outstanding_lock, flags);
  		}
  	}


Thanks,

Bart.