SMP in 32-bit arch/powerpc
benh at kernel.crashing.org
Thu Aug 17 09:12:48 EST 2006
On Wed, 2006-08-02 at 09:42 -0500, Jon Loeliger wrote:
> So, like, the other day Adrian Cox mumbled:
> > Is anybody else having problems with 32-bit SMP support in arch/powerpc?
> > I'm using 2.6.17 as my current base, because I've not yet merged the
> > latest mpic changes.
> > I'm currently bringing up a dual-7448 board, and when I build the kernel
> > with CONFIG_SMP, the bootmem allocator corrupts the device tree. The
> > strange thing is, this still happens when I don't start the second CPU.
> > Kernels built without CONFIG_SMP run flawlessly on the same hardware.
> As a point of reference, the 32-bit 8641 HPCN seems to be working fine
> with both CONFIG_SMP and the device tree mechanism in place. It was working
> both before and after the IRQ changes.
> Can you nail down any more specifics on how it is failing or where
> the corruption happens?
For completeness, there is a known bug with 32 bits and SMP regarding
icache coherency.... If you have random SIGILL/SEGV under load, that's
probably what you are hitting. The problem is due to the way we do the
coherency and isn't trivial to fix unfortunately, though it's also
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