Re: [RFC][PATCH] PM: Print a warning if firmware is requested when tasks are frozen

Greg KH
2011-05-02T23:15:38Z

On Tue, May 03, 2011 at 12:44:51AM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@sisk.pl>
>
> Some drivers erroneously use request_firmware() from their ->resume()
> (or ->thaw(), or ->restore()) callbacks, which is not going to work
> unless the firmware has been built in. This causes system resume to
> stall until the firmware-loading timeout expires, which makes users
> think that the resume has failed and reboot their machines
> unnecessarily. For this reason, make _request_firmware() print a
> warning when it has been called when tasks are frozen and it's
> impossible to start any new usermode helpers.
>
> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
> ---
> drivers/base/firmware_class.c | 3 +++
> include/linux/kmod.h | 1 +
> kernel/kmod.c | 8 ++++++++
> 3 files changed, 12 insertions(+)
>
> Index: linux-2.6/include/linux/kmod.h
> ===================================================================
> --- linux-2.6.orig/include/linux/kmod.h
> +++ linux-2.6/include/linux/kmod.h
> @@ -113,5 +113,6 @@ extern void usermodehelper_init(void);
>
> extern int usermodehelper_disable(void);
> extern void usermodehelper_enable(void);
> +extern bool usermodehelper_is_disabled(void);
>
> #endif /* __LINUX_KMOD_H__ */
> Index: linux-2.6/kernel/kmod.c
> ===================================================================
> --- linux-2.6.orig/kernel/kmod.c
> +++ linux-2.6/kernel/kmod.c
> @@ -301,6 +301,14 @@ void usermodehelper_enable(void)
> usermodehelper_disabled = 0;
> }
>
> +/**
> + * usermodehelper_is_disabled - check if new helpers are allowed to be started
> + */
> +bool usermodehelper_is_disabled(void)
> +{
> + return usermodehelper_disabled;
> +}
> +
> static void helper_lock(void)
> {
> atomic_inc(&running_helpers);
> Index: linux-2.6/drivers/base/firmware_class.c
> ===================================================================
> --- linux-2.6.orig/drivers/base/firmware_class.c
> +++ linux-2.6/drivers/base/firmware_class.c
> @@ -521,6 +521,9 @@ static int _request_firmware(const struc
> if (!firmware_p)
> return -EINVAL;
>
> + if (WARN_ON(usermodehelper_is_disabled()))
> + return -EBUSY;

But you can safely call this function with nowait set, and this warning
should not be triggered, right?

thanks,

greg k-h