Re: [PATCH v3] mmc: core: fix __mmc_switch timeout caused by preempt

[Ulf Hansson]

On 27 November 2015 at 02:41, Chaotian Jing <chaotian.jing@xxxxxxxxxxxx> wrote:
> there is a time window between __mmc_send_status() and time_afer(),
> on some eMMC chip, the timeout_ms is only 10ms, if this thread was
> scheduled out during this period, then, even card has already changes
> to transfer state by the result of CMD13, this part of code also treat
> it to timeout error.
> So, need calculate timeout first, then call __mmc_send_status(), if
> already timeout and card still in programing state, then treat it to
> the real timeout error.
>
> Signed-off-by: Chaotian Jing <chaotian.jing@xxxxxxxxxxxx>
> ---
>  drivers/mmc/core/mmc_ops.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
> index 1f44426..371aa4b 100644
> --- a/drivers/mmc/core/mmc_ops.c
> +++ b/drivers/mmc/core/mmc_ops.c
> @@ -489,6 +489,7 @@ int __mmc_switch(struct mmc_card *card, u8 set, u8 index, u8 value,
>         unsigned long timeout;
>         u32 status = 0;
>         bool use_r1b_resp = use_busy_signal;
> +       bool expired = false;
>
>         mmc_retune_hold(host);
>
> @@ -544,6 +545,12 @@ int __mmc_switch(struct mmc_card *card, u8 set, u8 index, u8 value,
>         /* Must check status to be sure of no errors. */
>         timeout = jiffies + msecs_to_jiffies(timeout_ms);
>         do {
> +               /*
> +                * Due to the possibility of being preempted after sending the
> +                * status command, check the expiration time first.
> +                */
> +               expired = time_after(jiffies, timeout);

The update of "expired" should have remained within the "if (send_status) {"

Please change that.

I realize that the entire __mmc_switch() function deserves a round of
re-factoring, as it's just too complicated to understand all what goes
on in here. That's another task though. :-)

> +
>                 if (send_status) {
>                         err = __mmc_send_status(card, &status, ignore_crc);
>                         if (err)
> @@ -565,12 +572,13 @@ int __mmc_switch(struct mmc_card *card, u8 set, u8 index, u8 value,
>                 }
>
>                 /* Timeout if the device never leaves the program state. */
> -               if (time_after(jiffies, timeout)) {
> +               if (expired && R1_CURRENT_STATE(status) == R1_STATE_PRG) {
>                         pr_err("%s: Card stuck in programming state! %s\n",
>                                 mmc_hostname(host), __func__);
>                         err = -ETIMEDOUT;
>                         goto out;
>                 }
> +
>         } while (R1_CURRENT_STATE(status) == R1_STATE_PRG);
>
>         err = mmc_switch_status_error(host, status);
> --
> 1.8.1.1.dirty
>

Kind regards
Uffe
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