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

Rafael J. Wysocki
2011-05-02T22:44:23Z

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;
+
*firmware_p = firmware = kzalloc(sizeof(*firmware), GFP_KERNEL);
if (!firmware) {
dev_err(device, "%s: kmalloc(struct firmware) failed\n",