Re: Change behaviour when tracing ... nasty trap (was Re: [PATCH] PM/Trace: get rid of synchronous resume limit during PM trace)

Rafael J. Wysocki
2015-01-26T13:18:21Z

On Monday, January 26, 2015 12:05:16 PM Pavel Machek wrote:
> On Mon 2015-01-26 10:39:04, Liu, Chuansheng wrote:
> > Hello Pavel,
> >
> > > > There are some kind of dependency between devices in some
> > > > hardware platforms. So, asynchronous resuming devices may
> > > > hang system due to wrong resume order. As a result, should
> > > > not fore synchronously resuming devices during tracing
> > > > PM events.
> > > >
> > > > Signed-off-by: Zhonghui Fu <zhonghui.fu@linux.intel.com>
> > > > ---
> > > > drivers/base/power/main.c | 3 +--
> > > > include/linux/resume-trace.h | 7 -------
> > > > 2 files changed, 1 insertions(+), 9 deletions(-)
> > > >
> > > > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> > > > index 9717d5f..5df148b 100644
> > > > --- a/drivers/base/power/main.c
> > > > +++ b/drivers/base/power/main.c
> > > > @@ -517,8 +517,7 @@ static int device_resume_noirq(struct device *dev,
> > > pm_message_t state, bool asyn
> > > >
> > > > static bool is_async(struct device *dev)
> > > > {
> > > > - return dev->power.async_suspend && pm_async_enabled
> > > > - && !pm_trace_is_enabled();
> > > > + return dev->power.async_suspend && pm_async_enabled;
> > > > }
> > > >
> > >
> > > Actually... whoever did the original patch was evil person. Changing
> > > behaviour when tracing is requested is evil, evil, evil. Git blame
> > > tells me
> > >
> > > Signed-off-by: Chuansheng Liu <chuansheng.liu@intel.com>
> > >
> > > went to the dark side.
> >
> > Although I didn't get where is something wrong, but the is_async() is not created by my commit,
> > it is from commit (PM: Start asynchronous resume threads upfront), I just moved it ahead.
> >
> > And like other phases, I added it into resum/suspend_noirq()...
>
> I see, blame blamed wrong person. It looks like Rafael is evil:
>
> commit 97df8c12995c5bac73e3bfeea4c5be155c1f4401
> Author: Rafael J. Wysocki <rjw@sisk.pl>
> Date: Sat Jan 23 22:25:31 2010 +0100
>
> PM: Start asynchronous resume threads upfront

This only means we won't use asyc suspend/resume at all when the RTC-based
resume debug is enabled, because it wouldn't make sense (the RTC-based
debug requires strict ordering of callbacks between devices or we may find
that device A hanged the resume while actually device B that was running in
parallel with A did that).

And I shouldn't even need to explain this ... Sad.

Rafael