On Thu, May 16, 2013 at 01:38:12PM +0200, Frederic Weisbecker wrote: > On Thu, May 16, 2013 at 10:10:27AM +0200, Peter Zijlstra wrote: > > On Wed, May 15, 2013 at 01:04:01PM -0400, Steven Rostedt wrote: > > > On Wed, 2013-05-15 at 18:59 +0200, Peter Zijlstra wrote: > > > > > > > At which point we could run the watchdog without perf_event_task_tick(). > > > > > > At which point we can drop the disable LOCKUP_DETECTOR when NO_HZ_FULL > > > is enabled ;-) > > > > > > > Can we? The thing I'm worried about is RCU (of course!). ISTR we rely on RCU > > working in NMI context. AFAIR for RCU to work, we need to come out of out > > magic > > NO_HZ state since that would've put RCU into EQS. > > > > Frederic, PaulMck? > > But they are protected inside rcu_nmi_*() functions, that's the only thing we > need. > If this interrupt userspace then we resume back to it quickly after the NMI > and > re-enter EQS. > > No need to restart the tick for that. A remote CPU that wants a quiescent > state > from the dyntick CPU will notice soon enough the EQS.
Right.. I just wasn't sure how much damage the RCU EQS stop/(re)start did to the entire NO_HZ_FULL situation. -- 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/
