Cross-CPU TLB flush problem with Fiasco.OC (r56, r58; exynos5)

Adam Lackorzynski adam at
Sun Sep 1 23:50:26 CEST 2013


On Wed Aug 28, 2013 at 20:59:37 +0200, Christian Prochaska wrote:
> I had a situation where CPU 1 accessed the wrong (same as before)
> physical memory location after it was idle while CPU 0 unmapped the
> memory page and mapped a different page at the same virtual address
> afterwards.
> When a CPU is idle, its TLB gets marked as 'inactive' in the kernel and
> the CPU doesn't receive cross-CPU TLB flush requests during this time.
> It seems there is a TLB flush missing somewhere after CPU 1 leaves the
> idle thread, to compensate for any missed flush requests during the idle
> time.
> When I added a 'Mem_unit::tlb_flush()' call after 'enable_tlb(cpu)' in
> 'Kernel_thread::idle_op()' as a test, this problem did not occur anymore.

Yes, you're right that's missing there.

Adam                 adam at

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