On Wed, 8 Oct 2014 10:03:36 +0100
Chris Wilson <ch...@chris-wilson.co.uk> wrote:
> and adding that back into the current build, e.g.
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 3632743..48a8a69 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -87,6 +87,7 @@ config X86
> select HAVE_USER_RETURN_NOTIFIER
> select ARCH_BINFMT_ELF_RANDOMIZE_PIE
> select HAVE_ARCH_JUMP_LABEL
> + select STOP_MACHINE
> select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
> select SPARSE_IRQ
> select GENERIC_FIND_FIRST_BIT
>
> fixes the regression.
>
Looking closer at this, it seems most configs work by accident,
because they have MOD_UNLOAD and/or HOTPLUG_CPU enabled. I take it
you disabled both of those? stop_machine() is called from all kinds
of places and almost none of them make sure STOP_MACHINE is selected.
$ find -name Kconf\* | xargs grep STOP_MACHINE
./init/Kconfig:config STOP_MACHINE
All these places use stop_machine():
mm/page_alloc.c, line 3886
drivers/xen/manage.c, line 130
drivers/char/hw_random/intel-rng.c, line 373
arch/powerpc/mm/numa.c:
line 1616
line 1623
arch/powerpc/platforms/powernv/subcore.c, line 324
arch/arm/kernel/kprobes.c, line 165
arch/arm/kernel/patch.c:
line 64
line 71
arch/s390/kernel/jump_label.c, line 61
arch/s390/kernel/kprobes.c:
line 311
line 320
arch/s390/kernel/time.c:
line 820
line 1590
arch/x86/kernel/cpu/mtrr/main.c, line 231
arch/arm64/kernel/insn.c, line 181
kernel/time/timekeeping.c, line 892
kernel/trace/ftrace.c, line 2219
kernel/module.c:
line 770
line 1861
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