Messages in this thread | | | Date | Thu, 25 Mar 2010 09:17:13 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH] Prevent nested interrupts when the IRQ stack is near overflowing v2 |
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On Thu, 25 Mar 2010, Linus Torvalds wrote: > > NOTE! Historically, the "fast" handlers also had a much faster irq > response because they didn't do that whole MASK/ACK/END thing. So they'd > just keep the CPU interrupts disabled, and ACK at the end, and I think > we've even used AUTOEIO so that they didn't need any ACK at all, and we > never touched the interrupt controller itself for them.
Btw, it was even more extreme than that. The fast irq handlers got a totally separate kernel entry point, and wouldn't save all registers, only the compiler-clobbered ones. Which is why they then had no "struct pt_regs" etc.
And yes, it really mattered. Then later we got so bloated that it wasn't much of an issue - and just made everything more complicated.
Linus
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