[PATCH] mmc: mediatek: fix race condition between msdc_request_timeout and irq

[PATCH] mmc: mediatek: fix race condition between msdc_request_timeout and irq

[Chaotian Jing]

when get request SW timeout, if CMD/DAT xfer done irq coming right now,
then there is race between the msdc_request_timeout work and irq handler,
and the host->cmd and host->data may set to NULL in irq handler. also,
current flow ensure that only one path can go to msdc_request_done(), so
no need check the return value of cancel_delayed_work().

Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>
---
 drivers/mmc/host/mtk-sd.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
index de09c6347524..898ed1b023df 100644
--- a/drivers/mmc/host/mtk-sd.c
+++ b/drivers/mmc/host/mtk-sd.c
@@ -1127,13 +1127,13 @@ static void msdc_track_cmd_data(struct msdc_host *host,
 static void msdc_request_done(struct msdc_host *host, struct mmc_request *mrq)
 {
 	unsigned long flags;
-	bool ret;
 
-	ret = cancel_delayed_work(&host->req_timeout);
-	if (!ret) {
-		/* delay work already running */
-		return;
-	}
+	/*
+	 * No need check the return value of cancel_delayed_work, as only ONE
+	 * path will go here!
+	 */
+	cancel_delayed_work(&host->req_timeout);
+
 	spin_lock_irqsave(&host->lock, flags);
 	host->mrq = NULL;
 	spin_unlock_irqrestore(&host->lock, flags);
@@ -1155,7 +1155,7 @@ static bool msdc_cmd_done(struct msdc_host *host, int events,
 	bool done = false;
 	bool sbc_error;
 	unsigned long flags;
-	u32 *rsp = cmd->resp;
+	u32 *rsp;
 
 	if (mrq->sbc && cmd == mrq->cmd &&
 	    (events & (MSDC_INT_ACMDRDY | MSDC_INT_ACMDCRCERR
@@ -1176,6 +1176,7 @@ static bool msdc_cmd_done(struct msdc_host *host, int events,
 
 	if (done)
 		return true;
+	rsp = cmd->resp;
 
 	sdr_clr_bits(host->base + MSDC_INTEN, cmd_ints_mask);
 
@@ -1363,7 +1364,7 @@ static void msdc_data_xfer_next(struct msdc_host *host,
 static bool msdc_data_xfer_done(struct msdc_host *host, u32 events,
 				struct mmc_request *mrq, struct mmc_data *data)
 {
-	struct mmc_command *stop = data->stop;
+	struct mmc_command *stop;
 	unsigned long flags;
 	bool done;
 	unsigned int check_data = events &
@@ -1379,6 +1380,7 @@ static bool msdc_data_xfer_done(struct msdc_host *host, u32 events,
 
 	if (done)
 		return true;
+	stop = data->stop;
 
 	if (check_data || (stop && stop->error)) {
 		dev_dbg(host->dev, "DMA status: 0x%8X\n",
-- 
2.18.0
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Re: [PATCH] mmc: mediatek: fix race condition between msdc_request_timeout and irq

[Ulf Hansson]

On Fri, 18 Dec 2020 at 08:16, Chaotian Jing <chaotian.jing@mediatek.com> wrote:
>
> when get request SW timeout, if CMD/DAT xfer done irq coming right now,
> then there is race between the msdc_request_timeout work and irq handler,
> and the host->cmd and host->data may set to NULL in irq handler. also,
> current flow ensure that only one path can go to msdc_request_done(), so
> no need check the return value of cancel_delayed_work().
>
> Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>

Applied for next, thanks!

Kind regards
Uffe


> ---
>  drivers/mmc/host/mtk-sd.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
> index de09c6347524..898ed1b023df 100644
> --- a/drivers/mmc/host/mtk-sd.c
> +++ b/drivers/mmc/host/mtk-sd.c
> @@ -1127,13 +1127,13 @@ static void msdc_track_cmd_data(struct msdc_host *host,
>  static void msdc_request_done(struct msdc_host *host, struct mmc_request *mrq)
>  {
>         unsigned long flags;
> -       bool ret;
>
> -       ret = cancel_delayed_work(&host->req_timeout);
> -       if (!ret) {
> -               /* delay work already running */
> -               return;
> -       }
> +       /*
> +        * No need check the return value of cancel_delayed_work, as only ONE
> +        * path will go here!
> +        */
> +       cancel_delayed_work(&host->req_timeout);
> +
>         spin_lock_irqsave(&host->lock, flags);
>         host->mrq = NULL;
>         spin_unlock_irqrestore(&host->lock, flags);
> @@ -1155,7 +1155,7 @@ static bool msdc_cmd_done(struct msdc_host *host, int events,
>         bool done = false;
>         bool sbc_error;
>         unsigned long flags;
> -       u32 *rsp = cmd->resp;
> +       u32 *rsp;
>
>         if (mrq->sbc && cmd == mrq->cmd &&
>             (events & (MSDC_INT_ACMDRDY | MSDC_INT_ACMDCRCERR
> @@ -1176,6 +1176,7 @@ static bool msdc_cmd_done(struct msdc_host *host, int events,
>
>         if (done)
>                 return true;
> +       rsp = cmd->resp;
>
>         sdr_clr_bits(host->base + MSDC_INTEN, cmd_ints_mask);
>
> @@ -1363,7 +1364,7 @@ static void msdc_data_xfer_next(struct msdc_host *host,
>  static bool msdc_data_xfer_done(struct msdc_host *host, u32 events,
>                                 struct mmc_request *mrq, struct mmc_data *data)
>  {
> -       struct mmc_command *stop = data->stop;
> +       struct mmc_command *stop;
>         unsigned long flags;
>         bool done;
>         unsigned int check_data = events &
> @@ -1379,6 +1380,7 @@ static bool msdc_data_xfer_done(struct msdc_host *host, u32 events,
>
>         if (done)
>                 return true;
> +       stop = data->stop;
>
>         if (check_data || (stop && stop->error)) {
>                 dev_dbg(host->dev, "DMA status: 0x%8X\n",
> --
> 2.18.0
>

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