Date: Thu, 25 Nov 2004 23:38:06 +0100
From: Pavel Machek <pavel@ucw.cz>
To: Nigel Cunningham <ncunningham@linuxmail.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Suspend 2 merge: 22/51: Suspend2 lowlevel code.
Message-ID: <20041125223806.GD2711@elf.ucw.cz>
References: <1101292194.5805.180.camel@desktop.cunninghams> <1101296166.5805.279.camel@desktop.cunninghams> <20041125183923.GK1417@openzaurus.ucw.cz> <1101420908.27250.71.camel@desktop.cunninghams>
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Hi!

> > > + * Note that the context and timing of this function is pretty critical.
> > > + * With a minimal amount of things going on in the caller and in here, gcc
> > > + * does a good job of being just a dumb compiler.  Watch the assembly output
> > > + * if anything changes, though, and make sure everything is going in the right
> > > + * place. 
> > 
> > You should include assembly source (unless you can test all the compilers...). Feel free
> > to include C version, too, but #ifdef it out.
> 
> I'm thinking I should actually be removing the comment. The C is simple,
> clear, fast and easy to maintain and we haven't actually had any
> problems at all with compilers. All my tweaking in here has turned out
> to be irrelevant to the real cause of problems (I recently found a bug
> where work queues were wrongly inheriting freezer flags; since fixing
> that, all the symptoms in this area have gone away).

See the flames I got when I did just that. No, it needs to be in
assembly, because (by standard) C compiler is allowed to misoptimize
it.
								Pavel
-- 
People were complaining that M$ turns users into beta-testers...
...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!
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