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 Tue, Feb 4, 2020 at 6:24 AM Lukasz Majewski <lukma@denx.de> wrote:
> >
> > 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.  
> 
> I'm not clear what you mean here, what should be changed?

timeval_long -> timeval long ?

> 
> >  
> > > ---
> > >  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.  
> 
> Yep, that's the plan :)
> 
> >
> > For ones with __WORDSIZE==32 it will be 32 bits instead. Am I
> > correct?  
> 
> Yes.
> 
> >  
> > > +  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.  
> 
> Ah ok. I'll remove the check from here.
> 
> >
> > 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);  
> 
> and I have added the check to here.

Thanks :-)

> 
> Alistair
> 
> >
> >  
> > > +  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
> >
> > --
> >
> > DENX Software Engineering GmbH,      Managing Director: Wolfgang
> > Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell,
> > Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> > lukma@denx.de  




Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de

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