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Date: Wed, 24 Jun 2009 03:32:33 -0700 (PDT) From: David Miller <davem@...emloft.net> To: andi@...stfloor.org Cc: linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org Subject: Re: NMI watchdog + NOHZ question From: Andi Kleen <andi@...stfloor.org> Date: Wed, 24 Jun 2009 12:23:25 +0200 >> And similarly to sparc64, if that 5+ second qla2xxx interrupt >> sequence happens after the tick_nohz_stop_sched_tick() call >> we can run into the same situation. > > Yes it would be probably safer to do the tick disabling with > interrupts off already. That only makes sense if you're really putting the cpu to sleep until an interrupt or similar happens. Here in this sparc64 case I'm not, I just spin waiting for the exit from cpu_idle() conditions. I'll think more about how I'll handle this. It's at least a relief to understand exactly what causes this issue now :-) > These days NMI watchdog is not used much on x86 anymore because it's > default off, so probably people never noticed that. I really didn't want to provide the feature that way on sparc64 which is why I made it on by default. It would be interesting to reconsider x86's default, perhaps even only on a trial basis in -next. It's so useful, and in the short time sparc64 has had this NMI code I can count at least 8 bugs I've fixed only because it was on all the time. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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