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SubjectRe: [PATCH] MMC: Fix race condition in resume/card detect code
On Mon, 20 Oct 2008 22:41:48 +0300, Yauhen Kharuzhy <jekhor@gmail.com> wrote:

> When device wakes up by card change interrupt and MMC_UNSAFE_RESUME is
> enabled then race condition between mmc_rescan() and
> mmc_resume()/mmc_sd_resume() appeared.
>
> Resume functions can sleep into mmc_remove_card() and at this time
> mmc_rescan() can be called by delayed work handler. Double-free of
> kobject or double-remove of host->card can be result of this.
>
> This patch adds an host->suspended flag which indicated that host is in
> suspend state. mmc_rescan() checks it and returned when
> host->suspended == 1. It's safe because resume code calls
> mmc_detect_change() at end of resume process.
>
> Signed-off-by: Yauhen Kharuzhy <jekhor@gmail.com>
> ---
> drivers/mmc/core/core.c | 7 +++++++
> include/linux/mmc/host.h | 3 +++
> 2 files changed, 10 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 044d84e..427f283 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -657,6 +657,9 @@ void mmc_rescan(struct work_struct *work)
> u32 ocr;
> int err;
>
> + if (host->suspended)
> + return;
> +
> mmc_bus_get(host);
>
> if (host->bus_ops == NULL) {
> @@ -780,6 +783,8 @@ int mmc_suspend_host(struct mmc_host *host, pm_message_t state)
>
> mmc_power_off(host);
>
> + host->suspended = 1;
> +
> return 0;
> }
>
> @@ -805,6 +810,8 @@ int mmc_resume_host(struct mmc_host *host)
> */
> mmc_detect_change(host, 1);
>
> + host->suspended = 0;
> +
> return 0;
> }
>
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 9c288c9..a584239 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -139,6 +139,9 @@ struct mmc_host {
> #ifdef CONFIG_MMC_DEBUG
> unsigned int removed:1; /* host is being removed */
> #endif
> +#ifdef CONFIG_MMC_UNSAFE_RESUME
> + unsigned int suspended:1;
> +#endif
>
> struct mmc_card *card; /* device attached to this host */
>

Shouldn't you also bracket any acces to ->suspended with the ifdefs ?
Compilation failed on my box...and I had to enable MMC_UNSAFE_RESUME.

--
J.A. Magallon <jamagallon()ono!com> \ Software is like sex:
\ It's better when it's free
Mandriva Linux release 2009.0 (Cooker) for i586
Linux 2.6.25-jam18 (gcc 4.3.1 20080626 (GCC) #1 SMP


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