On Tue, 2007-04-24 at 23:20 +0200, Andi Kleen wrote: > On Tuesday 24 April 2007 22:52:27 Daniel Walker wrote: > > On Tue, 2007-04-24 at 13:24 -0700, Jeremy Fitzhardinge wrote: > > > > > And sched_clock's use of local_irq_save/restore appears to be absolutely > > > correct, so I think it must be triggering a bug in either the self-tests > > > or lockdep itself. > > > > Why does sched_clock need to disable interrupts? > > It's only used in the instable path which is kind of "i already threw up > my hands" anyways > > I use it because when you transition from stable (TSC) to instable (jiffies) > the only way to avoid the clock jumping backwards is to remember and update > the > last value. To avoid races with parallel cpufreq handlers or timer > interrupts this small section needs to run with interrupts disabled.
Preemption is already disabled with the get_cpu_var() , so it seems like the timer interrupt is the only worry? I find it confusing that the access of jiffies_64 isn't protected from interrupts, it's only the per_cpu data which should already be protected by the get_cpu_var()/put_cpu_var .. Daniel - 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/
