linux-kernel - Re: gcc tickets for sparse attributes

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Message-ID: <1389954205.10404.1.camel@jlt4.sipsolutions.net>
Date:	Fri, 17 Jan 2014 11:23:25 +0100
From:	Johannes Berg <johannes@...solutions.net>
To:	Josh Triplett <josh@...htriplett.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Linux-Sparse <linux-sparse@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: gcc tickets for sparse attributes


> > IMHO the context extension doesn't work well enough in sparse to
> > document and implement as is. It would be much better if it actually was
> > able to differentiate between contexts, rather than treating each one
> > the same.
> 
> That would certainly be nice, but that's something actually much more
> easily done in GCC than in Sparse, given the types of information GCC
> already has available to implement features like alias analysis.

Right.

> In any case, the spec I wrote up assumes a distinction between contexts,
> but allows for an initial implementation like Sparse's that ignores the
> distinction.

Ok cool. :)

> > This would avoid the problem that locking one lock and
> > unlocking another (in the kernel's __acquire/ __release mechanism) could
> > still result in a warning.
> 
> That would actually *not* produce a warning, though it should.  In
> general, I *think* an implementation like Sparse's that ignores the
> distinction between locks should produce false negatives but not false
> positives.

Right, it doesn't report one now.

johannes

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