On Wed, 11 Sep 2013 10:25:45 -0400
Konrad Rzeszutek Wilk <konrad.w...@oracle.com> wrote:
> > It seems to imply line 53 is the originating bug, so that would be:
> >
> > 47 if (type == JUMP_LABEL_ENABLE) {
> > 48 /*
> > 49 * We are enabling this jump label. If it is not a nop
> > 50 * then something must have gone wrong.
> > 51 */
> > 52 if (unlikely(memcmp((void *)entry->code, ideal_nop, 5)
> > != 0))
> > 53 bug_at((void *)entry->code, __LINE__);
> >
> > But it is a NOP isn't it? The code is
> >
> > Unexpected op at trace_clock_global+0x6b/0x120 [ffffffff8113a21b] (0f 1f 44
> > 00 00) 53
> >
> > Perhaps the ideal_nop has not been set yet?
> >
>
> And this looks to fix it for me.
I'm trying to understand how this will fix it for you. Are you sure you
removed 'xen_nopvspin'?
If you are calling static_key_slow_inc() before jump_label_init(), then
it should still fail. The static_key_slow_inc() eventually calls
arch_jump_label_transform(), which calls __jump_label_transform() with
init == 0.
The below code looks to me that it would still compare the contents
with the ideal_nop, which hasn't been set yet.
-- Steve
>
> diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
> index ee11b7d..d688348 100644
> --- a/arch/x86/kernel/jump_label.c
> +++ b/arch/x86/kernel/jump_label.c
> @@ -44,13 +44,20 @@ static void __jump_label_transform(struct jump_entry
> *entry,
> union jump_code_union code;
> const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
>
> + if (init) {
> + const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
> + if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0))
> + bug_at((void *)entry->code, __LINE__);
> + }
> if (type == JUMP_LABEL_ENABLE) {
> /*
> * We are enabling this jump label. If it is not a nop
> * then something must have gone wrong.
> */
> - if (unlikely(memcmp((void *)entry->code, ideal_nop, 5) != 0))
> - bug_at((void *)entry->code, __LINE__);
> + if (!init) {
> + if (unlikely(memcmp((void *)entry->code, ideal_nop, 5)
> != 0))
> + bug_at((void *)entry->code, __LINE__);
> + }
>
> code.jump = 0xe9;
> code.offset = entry->target -
> @@ -62,11 +69,7 @@ static void __jump_label_transform(struct jump_entry
> *entry,
> * If this is the first initialization call, then we
> * are converting the default nop to the ideal nop.
> */
> - if (init) {
> - const unsigned char default_nop[] = {
> STATIC_KEY_INIT_NOP };
> - if (unlikely(memcmp((void *)entry->code, default_nop,
> 5) != 0))
> - bug_at((void *)entry->code, __LINE__);
> - } else {
> + if (!init) {
> code.jump = 0xe9;
> code.offset = entry->target -
> (entry->code + JUMP_LABEL_NOP_SIZE);
--
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