On 07/09/13 14:46, Konrad Rzeszutek Wilk wrote: > The xen_lock_spinning has a check for the kicker interrupts > and if it is not initialised it will spin normally (not enter > the slowpath). > > But for PVHVM case we would initialise the kicker interrupt > before the CPU came online. This meant that if the booting > CPU used a spinlock and went in the slowpath - it would > enter the slowpath and block forever. The forever part b/c
b/c? Ewww. Proper English please. > during bootup the interrupts are disabled - so the CPU would > never get an IPI kick and would stay stuck in the slowpath > logic forever. This description isn't right -- VCPUs blocked in SCHEDOP_poll can be unblocked on the event they're waiting for even if local irq delivery is disabled. > Why would the booting CPU never get an IPI kick? B/c in both > PV and PVHVM we consult the cpu_online_mask to determine whether > the IPI should go to its CPU destination. Since the booting > CPU has not yet finished and set that flag, it meant that > if any spinlocks were taken before the booting CPU had gotten to: I can't find where the online mask is being checked in xen_send_IPI_one(). Is this really the reason why it didn't work? This fix looks fine but both the description and the comment need to be fixed/clarified. David -- 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/
