[PATCH] mips: work-around R10k ll/sc errata

[Joseph S. Myers]

On Wed, 29 Jun 2011, Ralf Baechle wrote:

> > I didn't get any sense of consensus in the previous discussion (which 
> > extended to at least Jan 2009) and several people there are rather more 
> > expert in the MIPS variants than me.  Perhaps someone would care to put 
> > together a compilation of all the points raised and explain how the patch 
> > addresses them or at least leaves things no worse off - in particular 
> > detailing the circumstances (compiler options) under which the patch 
> > results in any change to the code in glibc.
> 
> Do you have a pointer to that old discussion?

http://sourceware.org/ml/libc-ports/2008-10/msg00010.html
http://sourceware.org/ml/libc-ports/2008-11/subjects.html#00000
http://sourceware.org/ml/libc-ports/2009-01/subjects.html#00036

> To summarize, I think the patch should be applied but the mentioned issues
> may deserve documentation.

Thanks.  Maciej, do you have any comments on this latest patch?

> As more of a general question, Is there a point in eventually moving this
> sort of stuff into a VDSO?  It would allow the kernel to provide suitable
> definitions of common LL/SC constructs without having to modify glibc.

I don't think it's easy for GCC to generate calls to a vDSO directly from 
__sync_* intrinsics, and __sync_* intrinsics (or in future an 
implementation of the C1X and C++0X atomics functionality using new 
versions of those intrinsics) are what we want code to use.

-- 
Joseph S. Myers
joseph@codesourcery.com