RE: RCU bug with v3.17-rc3 ?

[David Laight]

From: Nathan Lynch
> On 10/10/2014 11:25 AM, Russell King - ARM Linux wrote:
> >
> > Right, so GCC 4.8.{1,2} are totally unsuitable for kernel building (and
> > it seems that this has been known about for some time.)
> 
> Looking at http://gcc.gnu.org/PR58854 it seems that all 4.8.x for x < 3
> are affected, as well as 4.9.0.
> 
> > We can blacklist these GCC versions quite easily.  We already have GCC
> > 3.3 blacklisted, and it's trivial to add others.  I would want to include
> > some proper details about the bug, just like the other existing entries
> > we already have in asm-offsets.c, where we name the functions that the
> > compiler is known to break where appropriate.
> 
> Before blacklisting anything, it's worth considering that simple version
> checks would break existing pre-4.8.3 compilers that have been patched
> for PR58854.  It looks like Yocto and Buildroot issued releases with
> patched 4.8.2 compilers well before the (fixed) 4.8.3 release.  I think
> the most we can reasonably do without breaking some correctly-behaving
> toolchains is to emit a warning.

Is it possible to compile a small code fragment and check the generated
code for the bug?
Possibly predicated on the broken version number to avoid false positives.

	David



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