* Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> [170717 05:40]: > On Sun, Jul 16, 2017 at 11:08:07PM -0700, Tony Lindgren wrote: > > * Alex Shi <alex.shi@xxxxxxxxxx> [170716 16:25]: > > > I reused the rcu_irq_enter_irqson() from RCU_NONIDLE to avoid this issue. > > > It works fine. > > > > > > Tony, Could you like to give a tested-by if this patch works for you. > > > > Yeah that keeps things booting for me with no splats so: > > > > Tested-by: Tony Lindgren <tony@xxxxxxxxxxx> > > > > In general, it seems we're missing the knowledge in Linux kernel > > of when the entire system is idle. Right now it seems that only > > cpuidle_coupled knows that? > > > > We could probably simplify things by adding some PM state for > > entire system idle. Then cpuidle code and timer code could use > > that to test when it's safe to do whatever the SoC needs to do > > to enter deeper power states. > > > > If we already have something like that, please do let me know :) > > Well, we used to have CONFIG_NO_HZ_FULL_SYSIDLE, which detected > full-system idle lazily so as to avoid scalability bottlenecks. > https://lwn.net/Articles/558284/ > > No one was using it, so I removed it last merge window. The > patch that removed it is at sysidle.2017.05.11a, which can > probably still be reverted cleanly. Or just use v4.11 or earlier. OK thanks for the pointer, for reference that commit is fe5ac724d81a ("rcu: Remove nohz_full full-system-idle state machine"). For a potential user, I think we could use it for example in cpuidle_enter_state_coupled() + omap_enter_idle_coupled() where we try to figure out if the system is fully idle before calling tick_broadcast_enter(). Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
