linux-kernel - Re: [PATCH] mmc: sdhci: Setting the host->mrq to NULL before executing tuning

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Date:	Tue, 26 Nov 2013 17:50:59 -0500
From:	Chris Ball <cjb@...top.org>
To:	Chuansheng Liu <chuansheng.liu@...el.com>
Cc:	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	chuanxiao.dong@...el.com
Subject: Re: [PATCH] mmc: sdhci: Setting the host->mrq to NULL before executing tuning

Hi Chuansheng,

On Tue, Nov 05 2013, Chuansheng Liu wrote:
> In function sdhci_request(), it is possible to do the tuning execution
> like below:
>
> sdhci_request() {
> 	spin_lock_irqsave(&host->lock, flags);
> 	host->mrq = mrq;
> 	...
> 	spin_unlock_irqrestore(&host->lock, flags);
>
> <=== Here it is possible one pending finish_tasklet get running
>      and it will operate the original mrq, and notified the mrq
>      is done, and causes memory corruption.
>
> 	sdhci_execute_tuning(mmc, tuning_opcode);
> 	spin_lock_irqsave(&host->lock, flags);
> 	host->mrq = mrq;
> ...
> }
>
> In the above race place, the original mrq should not be finished wrongly,
> so here before unlock the spinlock, we need to set the host->mrq to NULL
> to avoid this case.
>
> Signed-off-by: Liu, Chuansheng <chuansheng.liu@...el.com>
> ---
>  drivers/mmc/host/sdhci.c |    7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 7a7fb4f..c7a001a 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1391,6 +1391,13 @@ static void sdhci_request(struct mmc_host *mmc, struct mmc_request *mrq)
>  					mmc->card->type == MMC_TYPE_MMC ?
>  					MMC_SEND_TUNING_BLOCK_HS200 :
>  					MMC_SEND_TUNING_BLOCK;
> +
> +				/* Here we need to set the host->mrq to NULL,
> +				 * in case the penging finish_tasklet
> +				 * operates it wrongly.
> +				 */
> +				host->mrq = NULL;
> +
>  				spin_unlock_irqrestore(&host->lock, flags);
>  				sdhci_execute_tuning(mmc, tuning_opcode);
>  				spin_lock_irqsave(&host->lock, flags);

Thanks, pushed to mmc-next for 3.14.

- Chris.
-- 
Chris Ball   <cjb@...top.org>   <http://printf.net/>
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