SMP cache synchronisation

Daniel Hellstrom daniel at
Thu Oct 24 13:15:15 UTC 2013


 From code analysis and testing SMP on LEON I can see that when installing a trap handler the cache is not invalidated correctly on other CPUs then the CPU installing the new trap handler. In the 
single-core case this is correct, but for SMP we must flush all CPUs caches. I think this is a platform independent problem for all self-modifying code. On the LEON SMP we normally don't see this 
since since the bad traps that are installed are never taken.

My suggestion is that we use a IPI to signal to other CPUs to invalidate their instruction cache, and CPU requesting such a remote CPU(s) flush should wait until all remote CPUs signal that their 
cache has been invalidated. The cache library could be extended to support SMP. Perhaps is should not be a platform independednt IPI solution, but rather a libcpu/BSP specific implementation for 
implementing cache flush on another CPU?

What do think about this issue?

Daniel Hellstrom

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