Hi. Today I noticed by accident that starting from Aug 4 (at least) all my emails went to nowhere. I am resending some of them...
Peter, Ingo, could you help? See the question about nmi at the end. On 08/03, Sebastian Andrzej Siewior wrote: > > On 08/03/2012 07:38 PM, Oleg Nesterov wrote: >>>> update_debugctlmsr(debugctl); >>>> + local_irq_enable(); >>> >>> wouldn't preempt_disable() be enough? >> >> preempt_disable() can't help if interrupt handler changes >> other bits in between? > > So perf() uses this register as well. Since perf() uses the raw > primitives (raw_spin_lock()) Hmm. perf/whatever uses raw_spin_lock() if the lock is raw_spinlock_t. But this doesn't matter? Whatever irq handler does has nothing to do with the problem, either local_irq_disable() can prevent this irq from happening, or not. > shouldn't you do the same? raw_local_irq_disable? I don't think so. > If I recall > correctly (but it is Friday and late) local_irq_enable() wouldn't > disable irqs on RT You mean it doesn't disable irqs in hardware? Yet local_irq_disable() should protect against the interrupt handler. OK, I know nothing about RT kernel (unfortunately), perhaps it has other primitives, but > and perf takes the raw lock this certainly doesn't matter, afaics. And note that __switch_to_xtra() runs under local_irq_disable() too. However. It seems that perf (intel_pmu_handle_irq) can play with MSR_IA32_DEBUGCTLMSR bits in nmi? In this case local_irq_disable() can't help. Doesn't this mean __switch_to_xtra() has problems? Oleg. -- 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/
