Re: [PATCH] paravirt/locks: avoid modifying static key before jump_label_init()

[Juergen Gross <jgross@suse.com>]

On 25/10/17 06:26, Dou Liyang wrote:
> Hi Juergen,
> 
> At 10/23/2017 09:49 PM, Juergen Gross wrote:
>> Don't try to set the static virt_spin_lock_key to a value before
>> jump_label_init() has been called, as this will result in a WARN().
>>
>> Solve the problem by introducing a new lock_init() hook called after
>> jump_label_init() instead of doing the call inside of
>> smp_prepare_boot_cpu().
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> ---
>> Based on kernel/git/tip/tip.git locking/core
> 
> I also found that WARN() in tip tree.
> 
> IMO, adding a hook in start_kernel() is not elegant. It will
> affect other arches and increase the complexity of the system.
> 
> I like your original method.
> So, I try to fix it by moving the native_pv_lock_init() from
>  native_smp_prepare_boot_cpu() to native_smp_prepare_cpus().

Hmm, this might work, but the Xen case has to be modified (same for
my more general solution), as xen_init_spinlocks() is still modifying
the static key too early. And we can't move xen_init_spinlocks() to
smp_prepare_cpus() as this would be too late for the alternatives
patching.

So let me extend your patch a little bit to cover Xen, too.

> I hope it's useful to you.

It really is, thanks.


Juergen