Hi Haijun,
On 21 August 2013 12:44, Haijun Zhang <Haijun.Zhang@xxxxxxxxxxxxx> wrote:
> When card is in cpu polling mode to detect card present. Card detecting
> task will be scheduled about once every second. When card is busy in large
> file transfer, detecting task will be hang and call trace will be prompt.
> In this case, when card is busy assume that card is present and just return
> in detecting task. Only polling card in case card is free to reduce conflict
> with data transfer.
>
> <7>mmc0: req done (CMD13): 0: 00000e00 00000000 00000000 00000000
> INFO: task kworker/u:1:12 blocked for more than 120 seconds.
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> kworker/u:1 D 00000000 0 12 2 0x00000000
> Call Trace:
> [ee06dd50] [44042028] 0x44042028
> (unreliable)
> [ee06de10] [c0007a0c] __switch_to+0xa0/0xf0
> [ee06de30] [c04dd50c] __schedule+0x1f8/0x4a4
>
> [ee06dea0] [c04dd898] schedule+0x30/0xbc
>
> [ee06deb0] [c03816a4] __mmc_claim_host+0x98/0x19c
>
> [ee06df00] [c0385f88] mmc_sd_detect+0x38/0xc0
>
> [ee06df10] [c0382b0c] mmc_rescan+0x294/0x2e0
> [ee06df40] [c00661cc] process_one_work+0x140/0x3e0
>
> [ee06df70] [c0066bf8] worker_thread+0x18c/0x36c
> [ee06dfb0] [c006bf10] kthread+0x7c/0x80
>
> [ee06dff0] [c000de58] kernel_thread+0x4c/0x68
> <7>sdhci [sdhci_irq()]: *** mmc0 got interrupt: 0x00000001
>
> Signed-off-by: Haijun Zhang <haijun.zhang@xxxxxxxxxxxxx>
> ---
> drivers/mmc/core/core.c | 5 +++++
> drivers/mmc/core/mmc.c | 3 ++-
> drivers/mmc/core/sd.c | 3 ++-
> drivers/mmc/core/sdio.c | 3 ++-
> 4 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 49a5bca..d51d9bd 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -924,15 +924,20 @@ EXPORT_SYMBOL(__mmc_claim_host);
> */
> int mmc_try_claim_host(struct mmc_host *host)
> {
> + struct mmc_card *card;
> int claimed_host = 0;
> unsigned long flags;
>
> + card = host->card;
> + pm_runtime_get_sync(&card->dev);
This wont work since it very well might trigger a mmc_claim_host,
which mean you will not be "trying" any more.
> +
> spin_lock_irqsave(&host->lock, flags);
> if (!host->claimed || host->claimer == current) {
> host->claimed = 1;
> host->claimer = current;
> host->claim_cnt += 1;
> claimed_host = 1;
> + set_current_state(TASK_RUNNING);
> }
> spin_unlock_irqrestore(&host->lock, flags);
> if (host->ops->enable && claimed_host && host->claim_cnt == 1)
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 6d02012..90e5555 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1447,7 +1447,8 @@ static void mmc_detect(struct mmc_host *host)
> BUG_ON(!host);
> BUG_ON(!host->card);
>
> - mmc_get_card(host->card);
> + if (!mmc_try_claim_host(host))
> + return;
>
I believe this is not a safe solution. You will solve the 120s hang
timeout, but you will instead invent a possible glitch for were a card
will not be removed when it should be.
Look into this sequence:
-> block layer handles request (mmc_get_card has been done)
-> block layer do error handling
-> mmc_detect_card_removed
-> mmc_detect_change is triggered to as soon as possible remove the card.
Then we have race, if the rescan job will run before the block layer
has fully completed mmc_put_card (which also involves a runtime auto
suspend of the card), the card might not be removed.
I think we need to make another solution here, could you maybe prevent
the polling rescan to be re-scheduled once the block layer is
operating on request? Using the runtime pm callbacks maybe? Could that
work?
Kind regards
Ulf Hansson
> /*
> * Just check if our card has been removed.
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index 176d125..6aae8d1 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -1042,7 +1042,8 @@ static void mmc_sd_detect(struct mmc_host *host)
> BUG_ON(!host);
> BUG_ON(!host->card);
>
> - mmc_get_card(host->card);
> + if (!mmc_try_claim_host(host))
> + return;
>
> /*
> * Just check if our card has been removed.
> diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
> index 80d89cff..e0cabf5 100644
> --- a/drivers/mmc/core/sdio.c
> +++ b/drivers/mmc/core/sdio.c
> @@ -875,7 +875,8 @@ static void mmc_sdio_detect(struct mmc_host *host)
> }
> }
>
> - mmc_claim_host(host);
> + if (!mmc_try_claim_host(host))
> + return;
>
> /*
> * Just check if our card has been removed.
> --
> 1.8.0
>
>
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