[PATCH] power: suspend: Add suspend timeout handler

[<josephjang@google.com>]

> On Tue, Oct 20, 2020 at 08:15:38AM +0000, josephjang@google.com wrote:
> > > On Tue, Oct 20, 2020 at 02:22:26PM +0800, Joseph Jang wrote:
> > > > Add sleep timer and timeout handler to prevent device stuck during
> > > suspend/
> > > > resume process. The timeout handler will dump disk sleep task at  
> first
> > > > round timeout and trigger kernel panic at second round timeout.
> > > > The default timer for each round is defined in
> > > > CONFIG_PM_SLEEP_TIMER_TIMEOUT.
> > > >
> > > > Signed-off-by: Joseph Jang <josephjang@google.com>
> > > > ---
> > > >  MAINTAINERS                   |  2 +
> > > >  include/linux/console.h       |  1 +
> > > >  include/linux/suspend_timer.h | 90  
> +++++++++++++++++++++++++++++++++++
> >
> > > Why is this file in include/linux/ if you only ever call it from  
> one .c
> > > file?
> >
> > I just refer to include/linux/suspend.h and create a new header file in  
> the
> > same folder.
> > If you have a better location for the new header file, please feel free  
> to
> > let me know.

> Only put .h files that are needed by different .c files in the
> include/linux/ directory.  Otherwise it should be local to where the .c
> file is.
> Great, use that!

> > But we really hit the suspend hang issue that DPM_WATCHDOG cannot cover.

> What issue is that?

> > We propose a wide coverage debug feature like PM_SLEEP_MONITOR which
> > not only covers PM but also core PM hang issues.
> >
> > And DPM_WATCHDOG is for device driver power management in
> > drivers/base/power/main.c
> > and PM_SLEEP_MONITOR locate is for core power management in
> > kernel/power/suspend.c.
> > I think it is fine for users to select whether they need device PM only  
> or
> > not.

> How will a user know which they should use?

> Why not just fix whatever is wrong with the watchdog code instead of
> creating a new one?

> > > And why isn't the watchdog sufficient for you?  Why are you "open
> > > coding" a watchdog timer logic here at all???
> >
> > Yes, we refer to DPM_WATCHDOG to extend the watchdog debugging for core  
> PM.
> > Because we really hit a real case that was not covered by DPM_WATCHDOG.

> Then fix that!

> > I think PM_SLEEP_MONITOR is an extension debug feature from  
> DPM_WATCHDOG.

> Please just fix the watchdog, as obviously it is not working properly.
> Don't create something new because of that.

> thanks,

> greg k-h

Thank you Greq for promptly responding.
I am okay to fix the DPM_WATCHDOG feature, but would like to have quick  
sync up before start.
Could you help?


1. Can we change the kernel config name ?
DPM_WATCHDOG stands for Device Power Management.
We propose PM_SLEEP_MONITOR is to cover Core PM and Device PM.


2. Can we create a new data structure instead of using the following struct  
dpm_watchdog?
struct dpm_watchdog {
	struct device		*dev;
	struct task_struct	*tsk;
	struct timer_list	timer;
};

I list some reasons by following ...

static int device_resume(struct device *dev, pm_message_t state, bool async)
{
	pm_callback_t callback = NULL;
	const char *info = NULL;
	int error = 0;
	DECLARE_DPM_WATCHDOG_ON_STACK(wd);  <== dpm_watchdog use stack memory for  
watchdog timer struct, but sleep timer use global memory.

...<SNIP>

	if (!dpm_wait_for_superior(dev, async))
		goto Complete;

	dpm_watchdog_set(&wd, dev);  <== dpm_watchdog need "struct device", but  
sleep timer doesn't need it.
	device_lock(dev);

...<SNIP>

  Unlock:
	device_unlock(dev);
	dpm_watchdog_clear(&wd);

  Complete:
	complete_all(&dev->power.completion);

	TRACE_RESUME(error);

	return error;
}

Thank you,
Joseph.