Re: lockdep and threaded IRQs (was: ...)

Peter Zijlstra
2009-03-03T09:28:11Z

On Mon, 2009-03-02 at 18:37 -0800, David Brownell wrote:
> No. But I did get a non-response that didn't include any
> explanation, and relied totally on unfounded assertions
> combined with the presumption that someday IRQF_DISABLED
> will be forced on in all drivers.

Enabling IRQs in hardirq context is BAD because:

- IRQ handler nesting leads to stack overflow
- It gives the false impression its OK for IRQ handlers to be slow,
it is _NOT_, as you still generate horrible preemption latency.

Therefore IRQF_DISABLED _will_ be forced on everybody some day soon, and
I'll provide an IRQF_ENABLED for use by broken hardware only (and make a
TAINT flag for that too).