[PATCH v1] scsi: ufs: Fix race between shutdown and runtime resume flow

[Can Guo]

On 2020-11-19 14:29, Stanley Chu wrote:
> If UFS host device is in runtime-suspended state while
> UFS shutdown callback is invoked, UFS device shall be
> resumed for register accesses. Currently only UFS local
> runtime resume function will be invoked to wake up the host.
> This is not enough because if someone triggers runtime
> resume from block layer, then race may happen between
> shutdown and runtime resume flow, and finally lead to
> unlocked register access.
> 
> To fix this kind of issues, in ufshcd_shutdown(), use
> pm_runtime_get_sync() instead of resuming UFS device by
> ufshcd_runtime_resume() "internally" to let runtime PM
> framework manage the whole resume flow.
> 
> Fixes: 57d104c153d3 ("ufs: add UFS power management support")
> Signed-off-by: Stanley Chu <stanley.chu at mediatek.com>

Reviewed-by: Can Guo <cang at codeaurora.org>

> ---
>  drivers/scsi/ufs/ufshcd.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 80cbce414678..bb16cc04f106 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -8941,11 +8941,7 @@ int ufshcd_shutdown(struct ufs_hba *hba)
>  	if (ufshcd_is_ufs_dev_poweroff(hba) && ufshcd_is_link_off(hba))
>  		goto out;
> 
> -	if (pm_runtime_suspended(hba->dev)) {
> -		ret = ufshcd_runtime_resume(hba);
> -		if (ret)
> -			goto out;
> -	}
> +	pm_runtime_get_sync(hba->dev);
> 
>  	ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM);
>  out: