Re: [PATCH] kbuild, sparseirq: work around GCC bug with __weakaliases

[Ingo Molnar]

* Paul Mackerras <paulus@xxxxxxxxx> wrote:

> Ingo Molnar writes:
> 
> > * Ingo Molnar <mingo@xxxxxxx> wrote:
> > 
> > > > I recall David Howells had a similar issue with the bootparamter patch 
> > > > set. The workaround he used was to add a barrier(); call in the weak 
> > > > function to avoid the inline.
> > > 
> > > could we add some extra attribute to __weak that would have a similar 
> > > effect? Something like __attribute__((noinline)), or something silly 
> > > like __attribute__((deprecated)) - just to keep gcc from screwing up 
> > > __weak functions? Perhaps adding a section attribute would have a 
> > > similar effect? (putting weak definitions into an extra section is 
> > > probably helpful anyway)
> > 
> > I've applied the patch below to tip/irq/sparseirq - could someone with an 
> > affected GCC version please check whether this solves the crash?
> 
> I recall from discussions earlier that noinline doesn't fix the problem, 
> and I just tested a similar case and verified that adding noinline 
> doesn't stop some versions of gcc from inlining them.  The empty weak 
> functions in kernel/perf_counter.c were getting inlined by the cross-gcc 
> (gcc 4.1.1) I use for compiling powerpc kernels on my laptop, and adding 
> noinline doesn't help there.

hm, does Yinghai's patch below do the trick? (also in perfcounters/core 
and tip/master)

	Ingo

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