linux-kernel - Re: [PATCH v5 06/15] scsi: ufs: avoid exception event handler racing with PM callbacks

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Date:	Tue, 27 Oct 2015 14:57:56 -0000
From:	"Gilad Broner" <gbroner@...eaurora.org>
To:	"Yaniv Gardi" <ygardi@...eaurora.org>
Cc:	robherring2@...il.com, james.bottomley@...senpartnership.com,
	pebolle@...cali.nl, hch@...radead.org,
	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, santoshsy@...il.com,
	linux-scsi-owner@...r.kernel.org, subhashj@...eaurora.org,
	ygardi@...eaurora.org, gbroner@...eaurora.org,
	draviv@...eaurora.org,
	"Vinayak Holikatti" <vinholikatti@...il.com>,
	"James E.J. Bottomley" <jbottomley@...n.com>
Subject: Re: [PATCH v5 06/15] scsi: ufs: avoid exception event handler racing
 with PM callbacks

Reviewed-by: Gilad Broner <gbroner@...eaurora.org>

> If device raises the exception event in the response to the commands
> sent during the runtime/system PM callbacks, exception event handler
> might run in parallel with PM callbacks and may see unclocked register
> accesses. This change fixes this issue by not scheduling the exception
> event handler while PM callbacks are running.
>
> Signed-off-by: Subhash Jadavani <subhashj@...eaurora.org>
> Signed-off-by: Yaniv Gardi <ygardi@...eaurora.org>
>
> ---
>  drivers/scsi/ufs/ufshcd.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 573a8cb..0e54183 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -3145,7 +3145,20 @@ ufshcd_transfer_rsp_status(struct ufs_hba *hba,
> struct ufshcd_lrb *lrbp)
>  			scsi_status = result & MASK_SCSI_STATUS;
>  			result = ufshcd_scsi_cmd_status(lrbp, scsi_status);
>
> -			if (ufshcd_is_exception_event(lrbp->ucd_rsp_ptr))
> +			/*
> +			 * Currently we are only supporting BKOPs exception
> +			 * events hence we can ignore BKOPs exception event
> +			 * during power management callbacks. BKOPs exception
> +			 * event is not expected to be raised in runtime suspend
> +			 * callback as it allows the urgent bkops.
> +			 * During system suspend, we are anyway forcefully
> +			 * disabling the bkops and if urgent bkops is needed
> +			 * it will be enabled on system resume. Long term
> +			 * solution could be to abort the system suspend if
> +			 * UFS device needs urgent BKOPs.
> +			 */
> +			if (!hba->pm_op_in_progress &&
> +			    ufshcd_is_exception_event(lrbp->ucd_rsp_ptr))
>  				schedule_work(&hba->eeh_work);
>  			break;
>  		case UPIU_TRANSACTION_REJECT_UPIU:
> --
> 1.8.5.2
>
> --
> QUALCOMM ISRAEL, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
> --
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-- 
Qualcomm Israel, on behalf of Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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