On Mon, 25 Jun 2007 23:04:25 +0200, [EMAIL PROTECTED] wrote: > > I think the tricky part is that we do want to reserve perfctr1 even > > though the NMI watchdog is not active. This comes from the fact that > > the NMI watchdog knows about only one counter and if it can't get that > > one, it probably fails. By reserving it from the start, we ensure NMI > > watchdog will work when eventually activated. > > Can you enable it later on at all? It failed for me when I tried, > because it didn't know which hardware to use. Had to pass the kernel > parameter to make the proc files do anything. Seems like it has to be > enable at boot to work at all. > > And AFAICT we never unconditionally reserved a perfctr for the watchdog.
Yes you can dynamically enable/disable the NMI watchdog, at least if you booted with it enabled. > In 2.6.21 the nmi watchdog, if enabled, just reserved its perfctrs and > everything else had to deal with it. Since the cleanup, the watchdog > will release its perfctr when disabled, so another subsystem can grab > it. But that also means that that other subsystem must release it again > before you can reenable the watchdog. Which is the obvious and correct way to handle a shared resource. Keeping parts of the PMU HW permanently reserved whether or not the watchdog is enabled would be a BUG. /Mikael - 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/