Re: [PATCH] mmc: core: Fix deadlock when the CONFIG_MMC_UNSAFE_RESUME is not defined

Ulf Hansson
2011-11-22T15:44:03Z

Sujit Reddy Thumma wrote:
> mmc_suspend_host() tries to claim host during suspend
> and release it only when the bus suspend operation is
> compeleted. If CONFIG_MMC_UNSAFE_RESUME is defined and
> the host is flagged as removable, mmc_suspend_host()
> tries to remove the card. In this process, the file system
> sync can get blocked trying to acquire host which is already
> claimed by mmc_suspend_host() causing deadlock.
>
> Fix this deadlock by releasing host before ->remove() is called.
>
> Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>
> ---
> drivers/mmc/core/core.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 271efea..8adbadf 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2338,6 +2338,7 @@ int mmc_suspend_host(struct mmc_host *host)
> * We simply "remove" the card in this case.
> * It will be redetected on resume.
> */
> + mmc_do_release_host(host);

Instead of having an "else" below move mmc_do_release_host to be done
before "if (err == -ENOSYS || !host->bus_ops->resume)"

> if (host->bus_ops->remove)
> host->bus_ops->remove(host);
> mmc_claim_host(host);
> @@ -2346,8 +2347,9 @@ int mmc_suspend_host(struct mmc_host *host)
> mmc_release_host(host);
> host->pm_flags = 0;
> err = 0;
> + } else {
> + mmc_do_release_host(host);
> }

Remove else statement entirely.

> - mmc_do_release_host(host);
> } else {
> err = -EBUSY;
> }

Otherwise it looks good to me! Thanks, for fixing this issue!

Br
Ulf Hansson