Re: [Xen-devel] [PATCH 4/7] add nspin_sleep function to time manager

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Apr 04, 2018 at 03:50:51PM +0000, Pawel Wieczorkiewicz wrote:
> From: Paul Semel <phentex@xxxxxxxxx>

Missing commit log?

> Signed-off-by: Paul Semel <phentex@xxxxxxxxx>
> 
> cr https://code.amazon.com/reviews/CR-836539
> ---
>  common/time.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/common/time.c b/common/time.c
> index c80bc11..db28d78 100644
> --- a/common/time.c
> +++ b/common/time.c
> @@ -106,6 +106,24 @@ int gettimeofday(struct timeval *tp)
>      return 0;
>  }
>  
> +#if defined(__i386__)
> +static inline void nspin_sleep(uint32_t t)
> +#else
> +static inline void nspin_sleep(uint64_t t)
> +#endif
> +{
> +#if defined(__i386__)
> +    uint32_t curr = since_boot_time();
> +    uint32_t end = curr + t;
> +#else
> +    uint64_t curr = since_boot_time();
> +    uint64_t end = curr + t;
> +#endif

Again same comment as before regarding the 32 vs 64bit types.

You would probably want something like:

if ( end < curr )
    panic("end value overflows counter\n");

> +
> +    while ( curr < end )
> +        curr = since_boot_time();

And you likely want this to be:

while ( end < since_boot_time() )
    asm volatile ("pause");

I'm actually trying to add a "pause" instruction helper in:

https://marc.info/?l=xen-devel&m=152241364510840

Thanks, Roger.

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