Hi Guenter, On Wed, 19 Dec 2012 14:41:22 -0800, Guenter Roeck wrote: > On Wed, Dec 19, 2012 at 01:47:21PM -0800, Andrew Morton wrote: > > The changelog didn't describe the end-user visible effects of the bug. > > Please always include this information. Because... > > One observed effect is that the s2c_hwmon driver reports a value of 4198403 > instead of 0 if the ADC reads 0. > > Other impact is unpredictable. Problem is seen if the divisor is an unsigned > variable or constant and the dividend is less than (divisor/2).
Really? In my own testing, the problem only shows with dividend == 0, and even then, only when dividend is signed and divisor is not. DIV_ROUND_CLOSEST(5, 20U) returns 0 as expected, and so do DIV_ROUND_CLOSEST(0 / 20), DIV_ROUND_CLOSEST(0U / 20) and DIV_ROUND_CLOSEST(0U / 20U). Are your observations different? > > The patch is applicable to 3.7.x. Should we backport it? > > Yes. DIV_ROUND_CLOSEST is used throughout the kernel, and impact is > unpredictable. > > 3.6 needs it as well. -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
