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

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Date:	Tue, 4 Aug 2015 21:54:47 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Oliver Neukum <oneukum@...e.com>,
	Dave Chinner <david@...morbit.com>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Len Brown <len.brown@...el.com>, Len Brown <lenb@...nel.org>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Alan Stern <stern@...land.harvard.edu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 1/1] suspend: delete sys_sync()

On Fri 2015-07-10 01:22:55, Rafael J. Wysocki wrote:
> On Thursday, July 09, 2015 09:32:51 AM Oliver Neukum wrote:
> > On Thu, 2015-07-09 at 00:03 +0200, Rafael J. Wysocki wrote:
> > 
> > > Nothing and I'm not discussing that (I've said that already at least once in
> > > this thread).
> > > 
> > > What I'm questioning is the "why" of calling sys_sync() from the kernel.
> > 
> > That's strictly speaking two questions
> > 
> > 1. Why do it in the kernel
> > 
> > That is easy. It closes the window of a race condition.
> > 
> > 2. Why do it at all
> > 
> > In essence because the system becomes inactive. For example we say that
> > data hits the disk after 30s maximum. We cannot meet such a limit unless
> > we sync.
> 
> Absolute deadlines are not guaranteed to be met at all in general when
> system suspend is used, at least from the user space perspective, so the
> above is quite a bit of an overstretch.

Well, this particular deadline _was_ guaranteed before Len's patch,
and it is useful one, too:

"if notebook is not on, it is ok to pull the USB stick".

									Pavel
									-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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