On Fri, 22 Jun 2018, Geert Uytterhoeven wrote: > On Fri, Jun 22, 2018 at 2:49 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > > On Fri, 22 Jun 2018, Geert Uytterhoeven wrote: > > > For the common cases where 1000 is a multiple of HZ, or HZ is a multiple > > > of 1000, jiffies_to_msecs() never returns zero when passed a non-zero > > > time period. > > > > > > However, if HZ > 1000 and not an integer multiple of 1000 (e.g. 1024 or > > > 1200, as used on alpha and DECstation), jiffies_to_msecs() may return > > > zero for small non-zero time periods. This may break code that relies > > > on receiving back a non-zero value. > > > > > > jiffies_to_usecs() does not need such a fix, as <linux/jiffies.h> does > > > not support values of HZ larger than 12287, thus rejecting any > > > problematic huge values of HZ. > > > > Sorry, I'm not understanding that sentence at all. > > Sorry for being unclear. > > 1 jiffy can only be less than 1µs if HZ > 1000000. > But include/linux/jiffies.h checks if HZ >= 12288, and does #error otherwise. > In addition, there's a "BUILD_BUG_ON(HZ > USEC_PER_SEC)" in time.c Hmm, ok. Care to reword? > > > Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > > > > This lacks a stable tag, right? > > Up to the maintainer to add, isn't it? Yes and no. At least a hint that this has been broken by commit X or has been broken forever would be appreciated. Thanks, tglx
