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

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Message-ID: <4932758.cYVny4lmZN@vostro.rjw.lan>
Date:	Mon, 06 Jul 2015 15:59:15 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Pavel Machek <pavel@....cz>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Dave Chinner <david@...morbit.com>,
	Len Brown <lenb@...nel.org>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	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()

On Monday, July 06, 2015 01:06:45 PM Pavel Machek wrote:
> On Mon 2015-07-06 01:28:20, Rafael J. Wysocki wrote:
> > On Saturday, July 04, 2015 10:19:55 AM Alan Stern wrote:
> > > On Sat, 4 Jul 2015, Rafael J. Wysocki wrote:
> > > 
> > > > The only argument against dropping sys_sync() from the suspend code path
> > > > I've seen in this thread that I entirely agree with is that it may lead to
> > > > regressions, because we've done it practically forever and it may hide latent
> > > > bugs somewhere in block drivers etc.  Dropping it, though, is the only way
> > > > to see those bugs, if any, and if we want to ever fix them, we need to see
> > > > them.  That's why I think that it may be a good idea to allow people to
> > > > drop it if they are willing to accept some extra risk (via the kernel
> > > > command line, for example).
> > > 
> > > I'd be perfectly happy to have the sync selectable at runtime, one way 
> > > or another.  The three most reasonable options seem to be:
> > > 
> > > 	kernel command line
> > > 
> > > 	sysfs file
> > > 
> > > 	sysctl setting
> > > 
> > > The command line is less flexible (it can't be changed after booting).  
> > > Either of the other two would be fine with me.
> > 
> > We'll probably use a sysfs file (possibly plus a Kconfig option to set the
> > boot time default).
> 
> Android people can already do sync-less s2ram using existing
> interface. IMO they should just do it.
> 
> In any case, sysfs file + Kconfig is an overkill. We already have too
> many Kconfig options.

I don't think we can reach a general agreement on what's the *right* approach
with respect to the sys_sync() in the suspend code path, so the only way out
of this situation I can see is to make it configurable.

> There's not a single Android phone supported by mainline
> kernel. I'm sure they have bigger problems than Android setting
> default sysfs values...

But perhaps we'd like to change that?

Thanks,
Rafael

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