Am 16.12.2010 14:13, Thomas Gleixner wrote: > On Mon, 13 Dec 2010, Jan Kiszka wrote: >> + if (old_action && (old_action->flags & IRQF_ADAPTIVE) && >> + !(desc->irq_data.drv_status & IRQS_SHARED)) { >> + /* >> + * Signal the old handler that is has to switch to shareable >> + * handling mode. Disable the line to avoid any conflict with >> + * a real IRQ. >> + */ >> + disable_irq(irq); > > This is weird, really. I thought you wanted to avoid waiting for the > threaded handler to finish if it's on the fly. So this should be > disable_irq_nosync() or did you change your mind ? No, I did not. I wanted to avoid that we set MAKE_SHAREABLE while there might be another IRQ in flight. The handler that is called due to a real IRQ might misinterpret MAKE_SHAREABLE as "there is no real event" and perform the wrong steps (at least the current implementation for KVM would). However, I will rebase my patch over your series now and try to re-think this. The question is what could go wrong if we do not guarantee that MAKE_SHAREABLE and ordinary IRQ will always be distinguishable. If there is really nothing, specifically for the KVM scenario, we could even drop the disable/enable_irq. That would be also be nicer when thinking about potential delays of the already registered handler during this transitional phase. Jan
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