On Tue, 2013-03-19 at 13:29 +0100, David Engraf wrote: > Hello, > > I've triggered an overflow when using ktime_add_ns() on a 32bit > architecture not supporting CONFIG_KTIME_SCALAR. > > When passing a very high value for u64 nsec, e.g. 7881299347898368000 > the do_div() function converts this value to seconds (7881299347) which > is still to high to pass to the ktime_set() function as long. The result > in my case is a negative value. > > The problem on my system occurs in the tick-sched.c, > tick_nohz_stop_sched_tick() when time_delta is set to > timekeeping_max_deferment(). The check for time_delta < KTIME_MAX is > valid, thus ktime_add_ns() is called with a too large value resulting in > a negative expire value. This leads to an endless loop in the ticker code: > > time_delta: 7881299347898368000 > expires = ktime_add_ns(last_update, time_delta) > expires: negative value > > This error doesn't occurs on 64bit or architectures supporting > CONFIG_KTIME_SCALAR (e.g. ARM, x86-32). > > Best regards > - David > > Signed-off-by: David Engraf <david.eng...@sysgo.com> >
But check already exists for 64bit arches in ktime_set() -- 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/
