Re: [PATCH] kbuild, sparseirq: work around GCC bug with __weakaliases
From: Ingo Molnar
Date: Sat Dec 27 2008 - 06:00:45 EST
* 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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