RE: [PATCH 1/2] mmc: core: fix permanent sleep of mmcqd during card removal

[Seungwon Jeon <tgih.jun@samsung.com>]

On Monday, February 04, 2013, Subhash Jadavani wrote:
> On 1/30/2013 12:00 PM, Seungwon Jeon wrote:
> > Hi Konstantin.
> >
> > Could you check this patch with [2/2]?
> > [PATCH 2/2] mmc: block: don't start new request when the card is removed
> >
> > mmcqd is often sleeping with acquiring the claim(mmc_claim_host) when a card is removed.
> > As a result, mmc_rescan can be blocked for the insertion of a card newly. It's a dead lock.
> >
> > Thanks,
> > Seungwon Jeon
> >
> > On Tuesday, January 22, 2013, Seungwon Jeon wrote:
> >> This patch is derived from 'mmc: fix async request mechanism ...'.
> >> According as async transfer, a request is handled with twice mmc_start_req.
> >> When the card is removed, the request is actually not issued in the first
> >> mmc_start_req [__mmc_start_data_req]. And then mmc_wait_for_data_req_done
> >> will come in the next mmc_start_req. But there is no event for completions.
> >> wake_up_interruptible is needed in __mmc_start_data_req for the case of
> >> removed card.
> 
> Hi Seungwon,
> 
> I looked at this again and i guess there is something wrong with
> mmc_start_req() itself.
> As per your commit text, first call to mmc_start_req() calls the
> __mmc_start_data_req() function and __mmc_start_data_req() returns the
> -ENOMEDIUM error (as card is removed) without starting the request on
> host controller. so now in mmc_start_req(), "start_err" should be set.
> But currently mmc_start_req() incorrectly marks the "host->areq" to
> "areq" in even if the start_err is set which i guess is wrong. what do
> you think about it?
> 
> So how about this fix? I guess this is better and it should fix the
> deadlock issue as well. Do let me know you thoughts on this. If it looks
> reasonable, i can post the formal patch.

Hi Subhash,

I tested your fix, but there is still problem.
I didn't look into the reason.

Thanks,
Seungwon Jeon
> 
> 
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 39f28af..1aa7dbe 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -546,7 +546,7 @@ struct mmc_async_req *mmc_start_req(struct mmc_host
> *host,
> if ((err || start_err) && areq)
> mmc_post_req(host, areq->mrq, -EINVAL);
> 
> - if (err)
> + if (err || start_err)
> host->areq = NULL;
> else
> host->areq = areq;
> 
> Regards,
> Subhash
> 
> >>
> >> Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
> >> ---
> >>  drivers/mmc/core/core.c |    1 +
> >>  1 files changed, 1 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> >> index 8b3a122..997b257 100644
> >> --- a/drivers/mmc/core/core.c
> >> +++ b/drivers/mmc/core/core.c
> >> @@ -350,6 +350,7 @@ static int __mmc_start_data_req(struct mmc_host *host, struct mmc_request *mrq)
> >>  	mrq->host = host;
> >>  	if (mmc_card_removed(host->card)) {
> >>  		mrq->cmd->error = -ENOMEDIUM;
> >> +		mmc_wait_data_done(mrq);
> >>  		return -ENOMEDIUM;
> >>  	}
> >>  	mmc_start_request(host, mrq);
> >> --
> >> 1.7.0.4
> >
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