On 11/17/2011 10:18 AM, Adrian Hunter wrote:
> On 14/11/11 13:12, Per Forlin wrote:
>> Host is claimed as long as there are requests in the block queue
>> and all request are completed successfully. If an error occur release
>> the host in case someone else needs to claim it, for instance if the card
>> is removed during a transfer.
>>
>> Signed-off-by: Per Forlin <per.forlin@xxxxxxxxxxxxxx>
>> ---
>> drivers/mmc/card/block.c | 37 +++++++++++++++++++++++++++++--------
>> 1 files changed, 29 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
>> index c80bb6d..c21fd2c 100644
>> --- a/drivers/mmc/card/block.c
>> +++ b/drivers/mmc/card/block.c
>> @@ -1158,6 +1158,28 @@ static int mmc_blk_cmd_err(struct mmc_blk_data *md, struct mmc_card *card,
>> return ret;
>> }
>>
>> +/*
>> + * This function should be called to resend a request after failure.
>> + * Prepares and starts the request.
>> + */
>> +static inline struct mmc_async_req *mmc_blk_resend(struct mmc_card *card,
>> + struct mmc_queue *mq,
>> + struct mmc_queue_req *mqrq,
>> + int disable_multi,
>> + struct mmc_async_req *areq)
>> +{
>> + /*
>> + * Release host after failure in case the host is needed
>> + * by someone else. For instance, if the card is removed the
>> + * worker thread needs to claim the host in order to do mmc_rescan.
>> + */
>> + mmc_release_host(card->host);
>> + mmc_claim_host(card->host);
>
> Does this work? Won't the current thread win the race
> to claim the host again?
>
Good question. I've tested it and I haven't seen any cases where current has claimed the host again. Sujit has tested the patch as well.
But I can't say that your scenario can't happen. I will study the wake_up and wait_queue code to see if I can find the answer.
Thanks,
Per
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