Re: compat_sys_times() bogus until jiffies >= 0.

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On Wed, Nov 07, 2007 at 03:28:33PM -0800, Andrew Morton wrote:
On Wed, 7 Nov 2007 14:47:22 -0800 David Brown <[email protected]> wrote:

will return '-1' to user space and set the negated clock_t value to errno.

At minimum, perhaps it should return a sane errno value.

RETURN VALUE
      times()  returns  the  number of clock ticks that have elapsed since an
      arbitrary point in the past.  For Linux 2.4 and earlier this  point  is
      the  moment  the  system  was  booted.   Since Linux 2.6, this point is
      (2^32/HZ) - 300 (i.e., about 429 million) seconds  before  system  boot
      time.   The  return  value  may  overflow  the  possible  range of type
      clock_t.  On error, (clock_t) -1 is returned, and errno is  set  appro-
      priately.

The strange -1 behavior is enshrined in history.  I think a better answer
is to tell people to use getrusage() if they want a return result without
this problem.

Adding INITIAL_JIFFIES will fix the case where an embedded system is booted
up to run a test and then shut down, and the mask, although it causes
discontinuities periodically at least moves them away from the early boot.

INITIAL_JIFFIES was a good idea, but it is probably best to keep it inside
of the kernel.

David Brown
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