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    SubjectRe: [PATCH] sdio: fix suspend/resume regression
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    On Sat, 2010-10-23 at 12:09 +0200, Ohad Ben-Cohen wrote:
    > Hi Maxim,
    >
    > On Fri, Oct 22, 2010 at 1:47 AM, Maxim Levitsky <maximlevitsky@gmail.com> wrote:
    > > On Wed, 2010-10-13 at 09:31 +0200, Ohad Ben-Cohen wrote:
    > >> Fix SDIO suspend/resume regression introduced by
    > >> 4c2ef25fe0b847d2ae818f74758ddb0be1c27d8e "mmc: fix all hangs related to
    > >> mmc/sd card insert/removal during suspend/resume":
    > ...
    > >> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
    > >> index c94565d..515ff39 100644
    > >> --- a/drivers/mmc/core/core.c
    > >> +++ b/drivers/mmc/core/core.c
    > >> @@ -1682,6 +1682,19 @@ int mmc_suspend_host(struct mmc_host *host)
    > >> if (host->bus_ops && !host->bus_dead) {
    > >> if (host->bus_ops->suspend)
    > >> err = host->bus_ops->suspend(host);
    > >> + if (err == -ENOSYS || !host->bus_ops->resume) {
    > > This reintroduces the bug I fixed.
    > >
    > > if the CONFIG_MMC_UNSAFE_RESUME isn't set (and that is default
    > > unfortunately), the host->bus_ops->resume will be NULL (see core/mmc.c
    > > mmc_ops), and therefore card will be removed, that will trigger a block
    > > device removal, sync, and deadlock).
    >
    > Have you reproduced this or is it just a general concern ?
    Only a general concern.
    >
    > I'm asking this because if CONFIG_MMC_UNSAFE_RESUME isn't set, then
    > mmc_pm_notify() will remove the card and detach the bus.
    >
    > As a result, host->bus_ops will be unset, and host->bus_dead will be set.
    >
    > In this case, mmc_suspend_host() should skip the code you are concerned about.
    You are right here.
    There is a very unlikely case that suspend of sd/mmc card fails (with
    CONFIG_MMC_UNSAFE_RESUME set, and that will trigger the hang, but that
    currently isn't possible because both mmc_sd_suspend and mmc_suspend
    just return 0 unconditionally).

    Btw, two above functions are identical, so some refactoring won't hurt.

    So sorry for noise (and bug).

    Best regards,
    Maxim Levitsky





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