linux-kernel - Re: [PATCH 2/4] mmc: core: allow non-blocking form of mmc_claim

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Date:	Mon, 23 Mar 2015 10:58:24 +0100
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	NeilBrown <neilb@...e.de>
Cc:	Tony Lindgren <tony@...mide.com>,
	Andreas Fenkart <afenkart@...il.com>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	GTA04 owners <gta04-owner@...delico.com>,
	NeilBrown <neil@...wn.name>,
	linux-omap <linux-omap@...r.kernel.org>
Subject: Re: [PATCH 2/4] mmc: core: allow non-blocking form of mmc_claim_host

On 24 February 2015 at 03:42, NeilBrown <neilb@...e.de> wrote:
> Change the handling for the 'abort' flag so that if
> it is set, but we can claim the host, then do the claim,
> rather than aborting.
>
> When the abort is async this just means that a race between aborting
> an allowing a claim is resolved slightly differently.  Any
> code must already be able to handle 'abort' being set just as the host
> is claimed.
>
> This allows extra functionality.  If __mmc_claim_host() is called
> with an 'abort' pointer which is initialized to '1', it will effect a
> non-blocking 'claim'.
>
> Signed-off-by: NeilBrown <neil@...wn.name>
> ---
>  drivers/mmc/core/core.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 23f10f72e5f3..541c8903dc6b 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -912,10 +912,11 @@ int __mmc_claim_host(struct mmc_host *host, atomic_t *abort)
>                 spin_lock_irqsave(&host->lock, flags);
>         }
>         set_current_state(TASK_RUNNING);
> -       if (!stop) {
> +       if (!host->claimed || host->claimer == current) {

This seems risky in that regards that it will change the behaviour for
the sdio_irq_thread(). Did you check that?

I guess we could change the sdio_irq_thread() to read it's
sdio_irq_thread_abort value before trying to claim the host?

>                 host->claimed = 1;
>                 host->claimer = current;
>                 host->claim_cnt += 1;
> +               stop = 0;
>         } else
>                 wake_up(&host->wq);
>         spin_unlock_irqrestore(&host->lock, flags);
>
>

Kind regards
Uffe
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