Christoph Lameter wrote: > On Tue, 22 Sep 2009, Tejun Heo wrote: > >> +#ifdef CONFIG_SMP >> + . = ALIGN(PERCPU_PAGE_SIZE); >> + __cpu0_per_cpu = .; > > __per_cpu_start? > >> + . = . + PERCPU_PAGE_SIZE; /* cpu0 per-cpu space */ >> +#endif > > This is a statically sized per cpu area that is used by __get_cpu_var() > Data is access via a cpu specific memory mapping. How does this work when > the area grows beyond PERCPU_PAGE_SIZE? As far as I can see: It seems > that __get_cpu_var would then cause a memory fault? On ia64, the first chunk is fixed at PERCPU_PAGE_SIZE. It's something hardwired into the page fault logic and the linker script. Build will fail if the static + reserved area goes over PERCPU_PAGE_SIZE and in that case ia64 will need to update the special case page fault logic and increase PERCPU_PAGE_SIZE. The area reserved above is interim per-cpu area for cpu0 which is used between head.S and proper percpu area setup and will be ditched once initialization is complete. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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