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cpuidle: menu: Avoid overflows when computing variance

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The variance computation in get_typical_interval() may overflow if
the square of the value of diff exceeds the maximum for the int64_t
data type value which basically is the case when it is of the order
of UINT_MAX.

However, data points so far in the future don't matter for idle
state selection anyway, so change the initial threshold value in
get_typical_interval() to INT_MAX which will cause more "outlying"
data points to be discarded without affecting the selection result.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Rafael J. Wysocki 2019-02-27 14:35:50 +01:00
parent ef8006846a
commit 814b8797f9
1 changed files with 1 additions and 1 deletions
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drivers/cpuidle/governors/menu.c
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@ -186,7 +186,7 @@ static unsigned int get_typical_interval(struct menu_device *data,
unsigned int min, max, thresh, avg;
uint64_t sum, variance;
thresh = UINT_MAX; /* Discard outliers above this value */
thresh = INT_MAX; /* Discard outliers above this value */
again: