HELP: clock_gettime() problem?

[Joel Sherrill]

Alex wrote:

> Hi,
> 
> Do you know why clock_gettime() POSIX call always returns the same value?

I am always amazed at how no matter what question or problem someone
has, someone else will ask it a few days later.  It can go unasked
for years or a bug unnoticed for a long time and then... BAM! :)

This was discussed in this thread a few days ago

http://www.rtems.com/ml/rtems-users/2004/march/msg00013.html

You probably are missing the line to configure a clock device driver.
And with 10 millisecond clock ticks, you are also subject to this:

> FWIW the accuracy of the RTEMS timeofday is configurable
> in number of microseconds.  It defaults to 10 milliseconds.
> CONFIGURE_MICROSECONDS_PER_TICK is the macro.  When you
> do a gettimeofday() it only looks at whole clock ticks and
> does not touch the HW to determine any partial clock tick
> amounts.

I am willing to discuss an optional BSP specific hook to return
nanoseconds since the last clock tick if the general consensus
is that it is needed.

--joel

> See next example:
> 
> #include <bsp.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <time.h>
> 
> ...
> 
>   //GET START TIME
>   clock_gettime( CLOCK_REALTIME, &start );
>   
>   clock_getres(CLOCK_REALTIME, &resolution);
>   //Some active huge delay... 
>   for(j=0;j<100000;j++)
>   {
>     for(i=0;i<1000000;i++)
>       cI=cI%status;
>   }
> 
>   //GET STOP TIME
>   clock_gettime( CLOCK_REALTIME, &current );
> 
> ...
> 
> 
> Every time I execute the program I always get the following values:
> 
> start.tv_sec=567993600
> start.tv_nsec=0
> 
> current.tv_sec=567993600
> current.tv_nsec=0
> 
> Why?
> 
> Thanks a lot...
> 
> Alex
> 
> 
> PS1: rtems version=4.6; bsp=pc686; in a i686 computer
> PS2: the clock_getres(CLOCK_REALTIME,&resolution) call 
>      returns tv_sec=0, tv_nsec=10.000.000
> 
> 
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