Linus Torvalds wrote:
On Tue, 20 Mar 2007, Zachary Amsden wrote:void local_irq_restore(int enabled) { pda.intr_mask = enabled; /* * note there is a window here where softirqs are not processed by * the interrupt handler, but that is not a problem, since it will * get done here in the outer enable of any nested pair. */ if (enabled) local_bh_enable(); }Actually, this one is more complicated. You also need to actually enable hardware interrupts again if they got disabled by an interrupt actually occurring while the "soft-interrupt" was disabled.
Actually, I was thinking the irq handlers would just not mess around with eflags on the stack, just call the chip to ack the interrupt and re-enable hardware interrupts when they left, since that is free anyway with the iret. Maybe leaving irqs disabled is better.
Anyway, it really *should* be pretty damn simple. No need to disable preemption, there should be no events that can *cause* it, since all interrupts get headed off at the pass.. (the return-from-interrupt thng should already notice that it's returning to an interrupts-disabled section and not try to do any preemption). What did I miss?
I wasn't disabling preemption to actually disable preemption. I was just using bh_disable as a global hammer to stop softirqs (thus the irq replay tasklet) from running during the normal irq_exit path. Then, we can just use the existing software IRQ replay code, and I think barely any new code (queue_irq(), etc) has to be written.
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