liberte@uiucdcs.Uiuc.ARPA (07/13/85)
Index: etc/sa.c /sys/sys/kern_acct.c 4.2BSD Fix
Description:
Two separate bugs cause negative numbers to occasionally appear
in the k*sec field of accounting reports.
Repeat-By:
I was not terribly successful at reproducing these negative
numbers since it requires exceedingly large cpu times and/or
memory usage. But our users would manage to do it periodically.
With both fixes, I haven't seen any.
Description:
One bug in sa.c causes overflow because calculations are done
with float values instead of double values in three places. The
other bug in the kernal accounting, kern_acct.c, causes overflow
because an int is used instead of unsigned int to hold cpu time.
Making it unsigned doubles the maximum and keeps it positive,
though overflow is still possible.
Another bug makes `sa -u` give trash.
Fix:
The following diffs are from old to new.
In /usr/src/etc/sa.c
636c636
< printf("%3d%6.1fcp %6dmem %6dio %.14s\n",
---
> printf("%4d %6dcp %6dmem %6dio %.14s\n",
645c645
< up->us_imem += x * y;
---
> up->us_imem += x * (double)y;
650,651c650,651
< tp->p.imem += x * y;
< timem += x * y;
---
> tp->p.imem += x * (double)y;
> timem += x * (double)y;
In /sys/sys/kern_acct.c
67c71
< register int i;
---
> register unsigned int i; /* BUGFIX */
100c104,105 /* The following is someone else's bug fix */
< if (i = u.u_ru.ru_utime.tv_sec + u.u_ru.ru_stime.tv_sec)
---
> if (i = (u.u_ru.ru_utime.tv_sec + u.u_ru.ru_stime.tv_sec)*hz + /* BUGFIX */
> (u.u_ru.ru_utime.tv_usec + u.u_ru.ru_stime.tv_usec)/tick
/* BUGFIX */
Dan LaLiberte
liberte@uiucdcs.Uiuc.ARPA
ihnp4!uiucdcs!liberte