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SubjectRe: [PATCH] tracing: Fix TRACING_SUPPORT dependency

On Sat, 21 Mar 2009, Ingo Molnar wrote:

>
> * Anton Vorontsov <avorontsov@ru.mvista.com> wrote:
>
> > On Fri, Mar 20, 2009 at 08:57:43PM +0100, Ingo Molnar wrote:
> > >
> > > * Anton Vorontsov <avorontsov@ru.mvista.com> wrote:
> > >
> > > > On Fri, Mar 20, 2009 at 08:04:28PM +0100, Ingo Molnar wrote:
> > > > >
> > > > > * Anton Vorontsov <avorontsov@ru.mvista.com> wrote:
> > > > >
> > > > > > commit 40ada30f9621fbd831ac2437b9a2a399aad34b00 ("tracing: clean
> > > > > > up menu"), despite the "clean up" in its purpose, introduced
> > > > > > behavioural change for Kconfig symbols: we no longer able to
> > > > > > select tracing support on PPC32 (because IRQFLAGS_SUPPORT isn't
> > > > > > yet implemented).
> > > > >
> > > > > Could you please solve this by implementing proper
> > > > > irqflag-tracing support? It's been available upstream for almost
> > > > > three years. It's needed for lockdep support as well, etc.
> > > >
> > > > Breaking things via clean up patches is an interesting method of
> > > > encouraging something to implement. ;-)
> > > >
> > > > Surely I'll look into implementing irqflags tracing, but
> > > > considering that no one ever needed this for almost three years,
> > > > [...]
> > >
> > > Weird, there's no lockdep support?
> >
> > *ashamed*: apparently no such support currently exist for PPC32. ;-)
>
> Hm, do all the tracers even compile on ppc32 with your patch?
>
> We had periodic build failures on weird, unmaintained architectures
> that had no irqflags-tracing support and hence didnt know the
> raw_irqs_save/restore primitives ...
>
> I'm not trying to make things more difficult for you (and we can
> apply your patch if it builds fine and does not cause problems
> elsewhere), but there were some real downsides to not having proper
> irq APIs ...

Note, the issue is not with the hooks into local_irq_save/restore, but
with the entry.S code. That code is very sensitive where the irqs are
enabled and disabled.

-- Steve



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