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On Tue, Oct 20, 2020 at 09:01:05AM +0000, josephj...@google.com wrote:
> > On Tue, Oct 20, 2020 at 08:15:38AM +0000, josephj...@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 <josephj...@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.
That's fine.
> 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;
> };
Why not use the existing one?
>
> 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.
Then move it off of the stack.
>
> ...<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.
That's fine, what are you trying to optimize for?
> device_lock(dev);
>
> ...<SNIP>
>
> Unlock:
> device_unlock(dev);
> dpm_watchdog_clear(&wd);
>
> Complete:
> complete_all(&dev->power.completion);
>
> TRACE_RESUME(error);
>
> return error;
> }
Submit a patch that shows what you are doing and we will be glad to
review that.
thanks,
greg k-h
