On Tue, Aug 20, 2013 at 06:11:10PM +0200, Tomasz Figa wrote: > Sometimes it is necessary to fix interrupt affinity to an offline CPU, > for example in initialization of local timers. This patch modifies > .set_affinity() operation of irq-gic driver to fall back to any possible > CPU if no online CPU can be found in requested CPU mask. Err, this is a bad idea. If a CPU is offline, then it must not respond to interrupts. If you bind an interrupt to an offline CPU, and that device asserts its interrupt, what happens? It doesn't get serviced until that CPU comes back online, which may be a very long time. If, for example, that is your network device, it would mean your network stops operating. Worse, the network layer will time out and reset the ethernet device, trying to get things working (which it won't.) I think how I used to handle this case prior to genirq is that I fell back to any online CPU if the interrupt ended up only routed to offline CPUs, but when an offline CPU comes back, it could then be re-routed back to that CPU. In other words, the mask change was non-destructive. I think with genirq, such mask changes are destructive. -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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