Re: [PATCH 1/5] Add a global synchronization point for pvclock

Avi Kivity
2010-04-17T18:50:00Z

On 04/17/2010 09:48 PM, Avi Kivity wrote:
>
>>
>> +static u64 last_value = 0;
>
> Needs to be atomic64_t.
>
>> +
>> cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
>> {
>> struct pvclock_shadow_time shadow;
>> unsigned version;
>> cycle_t ret, offset;
>> + u64 last;
>>
>>
>> + do {
>> + last = last_value;
>
> Otherwise, this assignment can see a partial update.

On a 32-bit guest, that is.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.