linux-kernel - Re: [PATCH] Introduce down_try() so we can move away from down

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Message-ID: <alpine.LFD.1.10.0808011118560.3277@nehalem.linux-foundation.org>
Date:	Fri, 1 Aug 2008 11:22:12 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Paul Menage <menage@...gle.com>, linux-kernel@...r.kernel.org,
	Matthew Wilcox <matthew@....cx>,
	"Randy.Dunlap" <rdunlap@...otime.net>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH] Introduce down_try() so we can move away from
 down_trylock()

On Fri, 1 Aug 2008, Andrew Morton wrote:

> > 
> 
> The naming is pretty sad, but the inconsistent return value from
> down_trylock() drives me batshit.  It means that every time I ever look
> at any sort of trylock call I need to go back to the definition site to
> work out if it's the one which returns true or if it's the one which
> returns false.
> 
> It would be good to get that fixed.  And if we _do_ want to fix it, I
> don't see any alternative to creating a new function.

The alternative is to just get rid of "down_trylock()" entirely. Creatign 
a shadow function with a different return value is just going to confuse 
people even more than the current situation.

That's why I pointed out that all the current users (apart from the 
special console usage) really do look like prime candidates to just 
convert to mutexes.

Of course, regardless, _some_ of those have actually taken the 
down_trylock semantics. See

	#define usb_trylock_device(udev)    down_trylock(&(udev)->dev.sem)

so nothing gets rid of that ;)

But at least it should be possible to replace something like half the 
current users of down_trylock() by just teh trivial conversion to mutexes. 
Which would be a good thing regardless.

			Linus
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