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Regarding "fast" path for IRQ handling out of the idle loop
I would like to discuss a point related to "fast" path for IRQ handling out of
the idle loop for armv7.
This facility was added for arm as part of the following checkin:
"Implement a "fast" path for IRQ handling out of the idle
loop. Since we
are in SVC32 already we only need to save a few registers.
also simplified since we know we can't return to user-mode."
Normally, arm uses irq_entry() to process interrupts. But as part of the above
checkin, if arm is in idle loop, it uses irq_idle_entry. The motivation was as
explained as above.
The point I want to discuss is related to what happens if during irq_idle_entry
processing, a soft interrupt is posted. This may happen, for example, if clock
interrupt posts a soft clock interrupt.
It appears, in that case, the soft interrupt would not be processed as part of
irq_idle_entry processing. This is in contrast to irq_entry(), which processes
any pending soft interrupts towards the end of its processing. Hence it appears
irq_idle_entry may unnecessarily delay processing of soft interrupts.
Thanks and regards,
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