On Thu, 12 Sep 2013 22:29:44 -0400
Boris Ostrovsky <boris.ostrov...@oracle.com> wrote:
> From: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
>
> xen_init_spinlocks() currently calls static_key_slow_inc() before
> jump_label_init() is invoked. When CONFIG_JUMP_LABEL is set (which usually is
> the case) the effect of this static_key_slow_inc() is deferred until after
> jump_label_init(). This is different from when CONFIG_JUMP_LABEL is not set,
> in
> which case the key is set immediately. Thus, depending on the value of config
> option, we may observe different behavior.
>
> In addition, when we come to __jump_label_transform() from jump_label_init(),
> the key (paravirt_ticketlocks_enabled) is already enabled. On processors where
> ideal_nop is not the same as default_nop this will cause a BUG() since it is
> expected that before a key is enabled the latter is replaced by the former
> during initialization.
>
> To address this problem we need to move
> static_key_slow_inc(¶virt_ticketlocks_enabled) so that it is called
> after jump_label_init(). We also need to make sure that this is done before
> other cpus start to boot. early_initcall appears to be a good place to do so.
> (Note that we cannot move whole xen_init_spinlocks() there since pv_lock_ops
> need to be set before alternative_instructions() runs.)
>
Reviewed-by: Steven Rostedt <rost...@goodmis.org>
Peter,
This fixes a regression in 3.12 against xen. Please pull and push to
Linus sometime soon.
Thanks,
-- Steve
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
> Signed-off-by: Boris Ostrovsky <boris.ostrov...@oracle.com>
> ---
> arch/x86/xen/spinlock.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
> index 253f63f..d90628d 100644
> --- a/arch/x86/xen/spinlock.c
> +++ b/arch/x86/xen/spinlock.c
> @@ -267,11 +267,18 @@ void __init xen_init_spinlocks(void)
> return;
> }
>
> - static_key_slow_inc(¶virt_ticketlocks_enabled);
> -
> pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(xen_lock_spinning);
> pv_lock_ops.unlock_kick = xen_unlock_kick;
> }
> +static __init int xen_init_spinlocks_jump(void)
> +{
> + if (!xen_pvspin)
> + return 0;
> +
> + static_key_slow_inc(¶virt_ticketlocks_enabled);
> + return 0;
> +}
> +early_initcall(xen_init_spinlocks_jump);
>
> static __init int xen_parse_nopvspin(char *arg)
> {
--
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