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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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