[arm arch] local_irq_restore() does not play well with local_fiq_enable()

[Russell King - ARM Linux]

On Thu, Mar 20, 2014 at 07:54:02PM +0000, Jonathan Bell wrote:
> hcd_init:
> 	setup the FIQ state
> 	install the fiq handler
> 	enable_fiq(USB)
> 	local_fiq_enable()
> 	usb_add_hcd()

You're not supposed to use local_fiq_enable() to enable FIQs in a device
driver - they should already be enabled by this point.

There has been a hole in that where FIQs haven't been enabled in the
idle thread, but that's a bug which needs fixing.  Otherwise, you should
assume that FIQs are always unmasked everywhere except for any short
code sequences that are contained within a short local_fiq_disable()..
local_fiq_enable() block.

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