Re: [PATCH] MMC: fix a race between card-detect rescan and clock-gate

[Andrei Warkentin <andreiw@motorola.com>]

On Fri, Apr 15, 2011 at 1:08 PM, Guennadi Liakhovetski
<g.liakhovetski@gmx.de> wrote:
> Currently there is a race in the MMC core between a card-detect
> rescan work and the clock-gating work, scheduled from a command
> completion. Fix it by removing the dedicated clock-gating mutex and
> using the MMC standard locking mechanism instead.
>
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> Cc: Simon Horman <horms@verge.net.au>
> Cc: Magnus Damm <damm@opensource.se>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> ---
>  drivers/mmc/core/host.c  |    9 ++++-----
>  include/linux/mmc/host.h |    1 -
>  2 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 461e6a1..2b200c1 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -94,7 +94,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
>                spin_unlock_irqrestore(&host->clk_lock, flags);
>                return;
>        }
> -       mutex_lock(&host->clk_gate_mutex);
> +       mmc_claim_host(host);
>        spin_lock_irqsave(&host->clk_lock, flags);
>        if (!host->clk_requests) {
>                spin_unlock_irqrestore(&host->clk_lock, flags);
> @@ -104,7 +104,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host *host)
>                pr_debug("%s: gated MCI clock\n", mmc_hostname(host));
>        }
>        spin_unlock_irqrestore(&host->clk_lock, flags);
> -       mutex_unlock(&host->clk_gate_mutex);
> +       mmc_release_host(host);
>  }
>
>  /*
> @@ -130,7 +130,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
>  {
>        unsigned long flags;
>
> -       mutex_lock(&host->clk_gate_mutex);
> +       mmc_claim_host(host);
>        spin_lock_irqsave(&host->clk_lock, flags);
>        if (host->clk_gated) {
>                spin_unlock_irqrestore(&host->clk_lock, flags);
> @@ -140,7 +140,7 @@ void mmc_host_clk_ungate(struct mmc_host *host)
>        }
>        host->clk_requests++;
>        spin_unlock_irqrestore(&host->clk_lock, flags);
> -       mutex_unlock(&host->clk_gate_mutex);
> +       mmc_release_host(host);
>  }
>
>  /**
> @@ -215,7 +215,6 @@ static inline void mmc_host_clk_init(struct mmc_host *host)
>        host->clk_gated = false;
>        INIT_WORK(&host->clk_gate_work, mmc_host_clk_gate_work);
>        spin_lock_init(&host->clk_lock);
> -       mutex_init(&host->clk_gate_mutex);
>  }
>
>  /**
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index bcb793e..eb792cb 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -183,7 +183,6 @@ struct mmc_host {
>        struct work_struct      clk_gate_work; /* delayed clock gate */
>        unsigned int            clk_old;        /* old clock value cache */
>        spinlock_t              clk_lock;       /* lock for clk fields */
> -       struct mutex            clk_gate_mutex; /* mutex for clock gating */
>  #endif
>
>        /* host specific block data */
> --
> 1.7.2.5

I've looked at this when Guennadi sent the original email and it looks
good to me FWIW.

A