Bug in Posix clock_getres.c

[Joel Sherrill]

David Polock wrote:
> 
> Hi,
> 
> I've just started to take a look at rtems, version 4.5.0. I think I've found
> a bug in rtems-4.5.0/c/src/exec/posix/src/clockgetres.c. If the mailing list
> is not the right place for bug reports, please point me to the correct address.

It is the right place. :)  Here is the patch that was checked into the
development
branch a while back.  This patch will be included in 4.5.1.

diff -u -r1.2 -r1.3
--- clockgetres.c       2000/08/30 17:12:42     1.2
+++ clockgetres.c       2001/01/22 14:19:05     1.3
@@ -1,5 +1,5 @@
 /*
- *  $Id: clockgetres.c,v 1.2 2000/08/30 17:12:42 joel Exp $
+ *  $Id: clockgetres.c,v 1.3 2001/01/22 14:19:05 joel Exp $
  */

 #include <assert.h>
@@ -36,8 +36,11 @@
     case CLOCK_REALTIME:
     case CLOCK_PROCESS_CPUTIME:
     case CLOCK_THREAD_CPUTIME:
-      if ( res )
-        _POSIX_Interval_to_timespec( _TOD_Microseconds_per_tick, res );
+      if ( res ) {
+        res->tv_sec = _TOD_Microseconds_per_tick / 1000000;
+        res->tv_nsec = _TOD_Microseconds_per_tick * 1000;
+        /* _POSIX_Interval_to_timespec( _TOD_Microseconds_per_tick, res );  */
+      }
       break;

     default:                              

> ------------------
> Bug description:
> 
> The function clock_getres should calculate the resolution of a time unit. The
> result is stored in a timespec structure. The operating system stores the timer
> resolution in _TOD_Microseconds_per_tick.
> 
> clockgetres.c:40 reads:
> >> _POSIX_Interval_to_timespec( _TOD_Microseconds_per_tick, res );
> 
> The function _POSIX_Interval_to_timespec expects "ticks" and calculates the
> corresponding time in microsecons with the line
> >> usecs = ticks * _TOD_Microseconds_per_tick;
> 
> So the abstract effect of these calls is:
> >> res = _TOD_Microseconds_per_tick * _TOD_Microseconds_per_tick
> 
> So the returned clock resolution is the squared value of the real clock resolution.
> 
> ------------------
> Bug fix:
> 
> Change line 40 in clockgetres.c to:
> >> _POSIX_Interval_to_timespec( 1, res );
> 
> Best regards,
> 
>   David Polock

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel at OARcorp.com                 On-Line Applications Research
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