Re: [PATCH 2/6] time: Add a timeval with a long tv_sec and tv_usec

[Lukasz Majewski <lukma at denx dot de>]

Hi Alistair,

> On y2038 safe 32-bit systems the Linux kernel expects itimerval to
> use a 32-bit time_t, even though the other time_t's are 64-bit. To
> address this let's add a timeval_long struct to be used internally.
			   ^^^^^^^^^^ - I think that this shall be
			   updated.

> ---
>  include/time.h | 43 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
> 
> diff --git a/include/time.h b/include/time.h
> index d425c69ede..c2c05bb671 100644
> --- a/include/time.h
> +++ b/include/time.h
> @@ -388,6 +388,49 @@ timespec64_to_timeval64 (const struct
> __timespec64 ts64) return tv64;
>  }
>  
> +/* A version of 'struct timeval' with `long` time_t
> +   and suseconds_t.  */
> +struct __timeval32
> +{
> +  long tv_sec;         /* Seconds.  */

As __timeval32 will be used in e.g __setitimer64 (which in turn will be
aliased to setitimer on archs with __WORDSIZE==64 && __TIMESIZE==64)
long seems to be the best option as it will be 64 bits for those
machines.

For ones with __WORDSIZE==32 it will be 32 bits instead. Am I correct?

> +  long tv_usec;        /* Microseconds.  */
> +};
> +
> +/* Conversion functions for converting to/from __timeval32
> +.  If the seconds field of a __timeval32 would
> +   overflow, they write { INT32_MAX, 999999 } to the output.  */
> +static inline struct __timeval64
> +valid_timeval32_to_timeval64 (const struct __timeval32 tv)
> +{
> +  return (struct __timeval64) { tv.tv_sec, tv.tv_usec };
> +}
> +
> +static inline struct __timeval32
> +valid_timeval64_to_timeval32 (const struct __timeval64 tv64)
> +{
> +  if (__glibc_unlikely (tv64.tv_sec > (time_t) 2147483647))
> +    return (struct __timeval32) { 2147483647, 999999};

What is the purpose of this code?

The valid_* prefix shall indicate that the timeval64 will fit the
timeval32 and there is no need for any explicit check.

I would expect usage of this function as presented here:
https://patchwork.ozlabs.org/patch/1230884/

if (! in_time_t_range (tv64.tv_sec))
  {
    __set_errno (EOVERFLOW);
    return -1;
  }

  if (tv)
    *tv = valid_timeval64_to_timeval (tv64);


> +  return (struct __timeval32) { tv64.tv_sec, tv64.tv_usec };
> +}
> +
> +static inline struct timeval
> +valid_timeval32_to_timeval (const struct __timeval32 tv)
> +{
> +  return (struct timeval) { tv.tv_sec, tv.tv_usec };
> +}
> +
> +static inline struct timespec
> +valid_timeval32_to_timespec (const struct __timeval32 tv)
> +{
> +  return (struct timespec) { tv.tv_sec, tv.tv_usec * 1000 };
> +}
> +
> +static inline struct __timeval32
> +valid_timespec_to_timeval32 (const struct timespec ts)
> +{
> +  return (struct __timeval32) { (time_t) ts.tv_sec, ts.tv_nsec /
> 1000 }; +}
> +
>  /* Check if a value is in the valid nanoseconds range. Return true if
>     it is, false otherwise.  */
>  static inline bool




Best regards,

Lukasz Majewski

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