Re: [PATCH V2] mmc: core: Fix deadlock when the CONFIG_MMC_UNSAFE_RESUME is not defined

Chris Ball
2011-12-01T18:18:17Z

Hi,

On Tue, Nov 22 2011, 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>
>
> ---
> Changes in v2:
> - Addressed review comment from Ulf Hansson.
> ---
> drivers/mmc/core/core.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 271efea..950b97d 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2333,6 +2333,8 @@ int mmc_suspend_host(struct mmc_host *host)
> mmc_poweroff_notify(host);
> err = host->bus_ops->suspend(host);
> }
> + mmc_do_release_host(host);
> +
> if (err == -ENOSYS || !host->bus_ops->resume) {
> /*
> * We simply "remove" the card in this case.
> @@ -2347,7 +2349,6 @@ int mmc_suspend_host(struct mmc_host *host)
> host->pm_flags = 0;
> err = 0;
> }
> - mmc_do_release_host(host);
> } else {
> err = -EBUSY;
> }

Thanks very much, pushed to mmc-next for 3.2 with ACKs from Ulf and Linus.

- Chris.
--
Chris Ball <cjb@laptop.org> <http://printf.net/>
One Laptop Per Child