linux-kernel - Re: [PATCH 1/1] suspend: delete sys

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Date:	Wed, 1 Jul 2015 23:07:29 -0400
From:	Len Brown <lenb@...nel.org>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 1/1] suspend: delete sys_sync()

>> The _vast_ majority of systems using Linux suspend today are under
>> an Android user-space.  Android has no assumption that that suspend to
>> mem will necessarily stay suspended for a long time.
>
> Indeed, however your change was not android-specific, and it is not
> "comfortable" on x86-style hardware and usage patterns.

"comfortable on x86-style and usage patterns"?
If you mean "traditional" instead of "comfortable",
where "tradition" is based on 10-year old systems, then sure.

But today, my x86 Android tablet is quite "comfortable"
without a sys_sync() in the kernel suspend path.

No, this isn't Android specific, Android is just the highest-volume demand,
making it an obvious example.

Chrome is the #1 selling "x86-style" clamshell laptop.
Chrome is not only "comfortable" with fast suspend/resume,
the Chrome developers demand it.

> That said, as long as x86 will still try to safeguard my data during mem
> sleep/resume as it does today, I have no strong feelings about
> light/heavy-weight "mem" sleep being strictly a compile-time selectable
> thing, or a more flexible runtime-selectable behavior.

The observation here is that the kernel should not force every system
to sys_sync() on every suspend.  The only question is how to best
implement that.  The obvious solution was to delete this forced policy
from the kernel, and let user-space handle it.
Rafael has not agreed to push that obvious, though less-than-gentle
solution upstream, and so I'll re-send the historic patch
that allows distros to still sync like it is 1999, if they want to:-)

thanks,
Len Brown, Intel Open Source Technology Center
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