cpuidle: menu: Avoid overflows when computing variance
authorRafael J. Wysocki <rafael.j.wysocki@intel.com>
Wed, 27 Feb 2019 13:35:50 +0000 (14:35 +0100)
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>
Thu, 7 Mar 2019 09:54:22 +0000 (10:54 +0100)
commit814b8797f9863abc2877acf87f6be0f140d00139
tree6532d58be3f811a5f173ccbb4e6eeed798baf797
parentef8006846a3a97d9d8bf49e63dba948d0d2dbbf0
cpuidle: menu: Avoid overflows when computing variance

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>
drivers/cpuidle/governors/menu.c