Re: [PATCH v9 05/12] x86, mpx: on-demand kernel allocation of bounds tables

Ren Qiaowei
2014-10-27T03:20:35Z

On 10/24/2014 08:08 PM, Thomas Gleixner wrote:
> On Sun, 12 Oct 2014, Qiaowei Ren wrote:
>> + /*
>> + * Go poke the address of the new bounds table in to the
>> + * bounds directory entry out in userspace memory. Note:
>> + * we may race with another CPU instantiating the same table.
>> + * In that case the cmpxchg will see an unexpected
>> + * 'actual_old_val'.
>> + */
>> + ret = user_atomic_cmpxchg_inatomic(&actual_old_val, bd_entry,
>> + expected_old_val, bt_addr);
>
> This is fully preemptible non-atomic context, right?
>
> So this wants a proper comment, why using
> user_atomic_cmpxchg_inatomic() is the right thing to do here.
>

Well, we will address it.

Thanks,
Qiaowei