On Thu, Aug 09, 2007 at 07:06:23PM -0700, Andrew Morton wrote: > On Thu, 9 Aug 2007 19:00:40 -0700 "Paul E. McKenney" <[EMAIL PROTECTED]> > wrote: > > > On Fri, Aug 10, 2007 at 03:31:46AM +0200, Adrian Bunk wrote: > > > On Thu, Aug 09, 2007 at 01:51:06AM -0700, Andrew Morton wrote: > > > >... > > > > Changes since 2.6.23-rc2-mm1: > > > >... > > > > +allow-rcutorture-to-handle-synchronize_sched.patch > > > >... > > > > 2.6.23 queue > > > >... > > > > > > All drivers were converted to no longer use xtime directly since it > > > might be quite outdated, but this patch adds a usage of xtime.tv_nsec > > > as RNG... > > > > This code doesn't care if the time is outdated, as it is simply > > periodically perturbing an RNG, but OK. > > > > So, what interface are we supposed to be using instead? I cannot use > > get_random_bytes() due to locking issues. This is not a cryptographically > > secure usage, so the perturbation does not need to be extremely high > > quality. > > > > On x86, I would just grab the low-order bits of the TSC, but all of the > > world is not an x86. ;-) > > One used to use sched_clock() for this, then get frowned at. Now we > have cpu_clock()...
Hmmm... And cpu_clock() is not in 2.6.22, so must appear in some later release. Which means that the rate of API change in this area is a bit high, so I should avoid it like the plague. Therefore, I should look for some other convenient source of entropy. One convenient source would the per-CPU statistics that rcutorture maintains. Of course, a given CPU's RNG is nearly in lock-step with its own statistics, but not with the adjacent CPU's statistics... I will send a patch. Thanx, Paul - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/