On Tue, 2007-03-13 at 13:48 -0700, Jeremy Fitzhardinge wrote: > * init_gdt should always use write_gdt_entry when touching the gdt; > if it doesn't and it ends up touching an already-installed gdt > under Xen, it will get a write fault. This happens because > init_gdt ends up getting called twice in SMP (see below).
Hmm, this invalidated my assumption that write_gdt_entry is always a write to this cpu's active gdt. Better fix is not to call it twice anyway... > * init_gdt should always be called before bringing up the cpu, > rather than by the cpu itself (and therefore, cpu_init() shouldn't > call it). Obviously the the boot cpu is an exception. Makes sense. > * secondary_cpu_init stops being necessary. Indeed. > * On SMP, init_gdt can get called twice: first time in > smp_prepare_boot_cpu, and a second time in trap_init. On UP, > trap_init is the only caller. Getting rid of the call in smp_prepare_boot_cpu currently works, but it's fragile: __get_cpu_var(x) && per_cpu(x, smp_processor_id()) will differ, and changes made to __get_cpu_var(x) will vanish... Fortunately, UP doesn't have to call init_gdt at all, so I think it's better to place it in smp_prepare_boot_cpu only and then clean up the UP code. I'll try now... Rusty. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
