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Date: Sat, 21 Jul 2012 11:56:04 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Ming Lei <tom.leiming@...il.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"linux-usb" <linux-usb@...r.kernel.org>,
Alan Stern <stern@...land.harvard.edu>,
"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
Oliver Neukum <oneukum@...e.de>, Dave Jones <davej@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Matthew Garrett <mjg@...hat.com>,
Jack Stone <jwjstone@...tmail.fm>,
Larry Finger <Larry.Finger@...inger.net>,
Alan Cox <alan@...rguk.ukuu.org.uk>,
Ming Lei <ming.lei@...onical.com>
Subject: Re: [RFC] firmware load: defer request_firmware during early boot and resume
On Saturday, July 21, 2012, Ming Lei wrote:
> CC guys who discussed the problem in the below link in Jan. :
>
> http://marc.info/?t=132528956000002&r=10&w=2
>
> On Fri, Jul 20, 2012 at 8:33 PM, Ming Lei <tom.leiming@...il.com> wrote:
> > 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.
>
> Looks it works well in my two test cases: one is to call request_firmware
> in early boot(initcall), another one is to call request_firmware in probe()
> of resume path(caused by unbind & rebind). And without the patch, both
> two request_firmware return failure and can't complete the loading.
And that's precisely why you're not supposed to use request_firmware() in
those two situations.
My opinion is that, at least for the suspend/hibernate case, the firmware
data should be loaded into memory before suspend (e.g. using a PM notifier)
and released only after the corresponding resume (or suspend failure), so
that it's present in memory during the entire suspend-resume cycle.
The early bood situation may be handled through deferred probing.
Thanks,
Rafael
> V1:
> only defer handling the requests called from probe()
>
> 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..1b13536 100644
> --- a/drivers/base/firmware_class.c
> +++ b/drivers/base/firmware_class.c
> @@ -21,6 +21,7 @@
> #include <linux/firmware.h>
> #include <linux/slab.h>
> #include <linux/sched.h>
> +#include "base.h"
>
> #define to_dev(obj) container_of(obj, struct device, kobj)
>
> @@ -593,6 +594,11 @@ request_firmware(const struct firmware
> **firmware_p, const char *name,
> if (IS_ERR_OR_NULL(fw_priv))
> return PTR_RET(fw_priv);
>
> + /* only defer handling the requests called from probe() */
> + if (!klist_node_attached(&device->p->knode_driver) &&
> + 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..02fc1c2 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -809,6 +809,9 @@ static noinline int init_post(void)
> current->signal->flags |= SIGNAL_UNKILLABLE;
> flush_delayed_fput();
>
> + /* defer handling request_firmware in probe of initcall path */
> + 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..61c723f 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 +304,12 @@ static int enter_state(suspend_state_t state)
> Finish:
> pr_debug("PM: Finishing wakeup.\n");
> suspend_finish();
> +
> + system_state = SYSTEM_RUNNING;
> +
> + /* defer handling request_firmware in probe of resume path */
> + driver_deferred_probe_trigger();
> +
> Unlock:
> mutex_unlock(&pm_mutex);
> return error;
>
>
>
> Thanks,
>
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