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[POWERPC] Fix possible division by zero in scaled time accounting 

If we get no user time and no system time allocated since the last
account_system_vtime, the system to user time ratio estimate can end
up dividing by zero.

This was causing a problem noticed by Balbir Singh.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Michael Neuling 2007-11-20 15:18:40 +11:00 committed by Paul Mackerras
parent c443acab2e
commit 2b46b5673c
1 changed files with 3 additions and 2 deletions
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5
arch/powerpc/kernel/time.c
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@ -241,8 +241,9 @@ void account_system_vtime(struct task_struct *tsk)
/* deltascaled includes both user and system time.
* Hence scale it based on the purr ratio to estimate
* the system time */
deltascaled = deltascaled * get_paca()->system_time /
(get_paca()->system_time + get_paca()->user_time);
if (get_paca()->user_time)
deltascaled = deltascaled * get_paca()->system_time /
(get_paca()->system_time + get_paca()->user_time);
delta += get_paca()->system_time;
get_paca()->system_time = 0;
}