Re: [Xen-devel] [PATCH v2 5/6] x86/time: refactor read_platform_stime()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.03.16 at 15:44, <joao.m.martins@xxxxxxxxxx> wrote:
> -static s_time_t read_platform_stime(void)
> +static s_time_t read_platform_stime(u64 *stamp)
>  {
> -    u64 count;
> +    u64 plt_stamp_counter, count;

"stamp" and "counter" seem kind of redundant.

>      s_time_t stime;
>  
>      ASSERT(!local_irq_is_enabled());
>  
>      spin_lock(&platform_timer_lock);
> -    count = plt_stamp64 + ((plt_src.read_counter() - plt_stamp) & plt_mask);
> +    plt_stamp_counter = plt_src.read_counter();
> +    count = plt_stamp64 + ((plt_stamp_counter - plt_stamp) & plt_mask);
>      stime = __read_platform_stime(count);
> +    if ( stamp )
> +        *stamp = plt_stamp_counter;
>      spin_unlock(&platform_timer_lock);

What reason is there to do that conditional write inside the locked
region?

Jan


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