linux-kernel - [RFC] firmware load: defer request_firmware during early boot and resume

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Date:	Fri, 20 Jul 2012 20:33:32 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-usb <linux-usb@...r.kernel.org>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Oliver Neukum <oneukum@...e.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: [RFC] firmware load: defer request_firmware during early boot and resume

The RFC patch is just for discussing if the idea of deferring
request_firmware is doable for addressing the issue of
request_firmware in resume path, which is caused by driver
unbind/rebind during resume.

At least usb bus is involved in such things, one driver may be
unbound and rebound in resume path at several situations, and
request_firmware is often called inside probe().

Also the idea should be helpful for other hotplug buses too,
at least there was the similar problem report on pcmcia bus.

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 6cd2c6c..fb02eff 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -123,7 +123,7 @@ static bool driver_deferred_probe_enable = false;
  * list and schedules the deferred probe workqueue to process them.  It
  * should be called anytime a driver is successfully bound to a device.
  */
-static void driver_deferred_probe_trigger(void)
+void driver_deferred_probe_trigger(void)
 {
 	if (!driver_deferred_probe_enable)
 		return;
@@ -144,6 +144,7 @@ static void driver_deferred_probe_trigger(void)
 	 */
 	queue_work(deferred_wq, &deferred_probe_work);
 }
+EXPORT_SYMBOL_GPL(driver_deferred_probe_trigger);

 /**
  * deferred_probe_initcall() - Enable probing of deferred devices
diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index 5401814..4fe742f 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -593,6 +593,9 @@ request_firmware(const struct firmware
**firmware_p, const char *name,
 	if (IS_ERR_OR_NULL(fw_priv))
 		return PTR_RET(fw_priv);

+	if (system_state != SYSTEM_RUNNING)
+		return -EPROBE_DEFER;
+
 	ret = usermodehelper_read_trylock();
 	if (WARN_ON(ret)) {
 		dev_err(device, "firmware: %s will not be loaded\n", name);
diff --git a/include/linux/device.h b/include/linux/device.h
index d0e4d99..a63d3171 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -244,7 +244,7 @@ extern struct device_driver *driver_find(const char *name,
 					 struct bus_type *bus);
 extern int driver_probe_done(void);
 extern void wait_for_device_probe(void);
-
+extern void driver_deferred_probe_trigger(void);

 /* sysfs interface for exporting driver attributes */

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index e07f5e0..c8d74c6 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -378,6 +378,7 @@ extern enum system_states {
 	SYSTEM_POWER_OFF,
 	SYSTEM_RESTART,
 	SYSTEM_SUSPEND_DISK,
+	SYSTEM_SUSPEND,
 } system_state;

 #define TAINT_PROPRIETARY_MODULE	0
diff --git a/init/main.c b/init/main.c
index e60679d..237eae1 100644
--- a/init/main.c
+++ b/init/main.c
@@ -809,6 +809,8 @@ static noinline int init_post(void)
 	current->signal->flags |= SIGNAL_UNKILLABLE;
 	flush_delayed_fput();

+	driver_deferred_probe_trigger();
+
 	if (ramdisk_execute_command) {
 		run_init_process(ramdisk_execute_command);
 		printk(KERN_WARNING "Failed to execute %s\n",
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 1da39ea..dbf6ffb 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -224,6 +224,9 @@ int suspend_devices_and_enter(suspend_state_t state)
 		goto Recover_platform;
 	}
 	suspend_test_finish("suspend devices");
+
+	system_state = SYSTEM_SUSPEND;
+
 	if (suspend_test(TEST_DEVICES))
 		goto Recover_platform;

@@ -301,6 +304,10 @@ static int enter_state(suspend_state_t state)
  Finish:
 	pr_debug("PM: Finishing wakeup.\n");
 	suspend_finish();
+
+	system_state = SYSTEM_RUNNING;
+	driver_deferred_probe_trigger();
+
  Unlock:
 	mutex_unlock(&pm_mutex);
 	return error;


Thanks,
-- 
Ming Lei
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