Hi all,

Forgive me if this is a silly question because it is documented somewhere, but I am unfamiliar with Fiasco source, and too in a hurry to go through all the Fiasco source code and cross-comare it with the documentation/papers/examples etc....

Skimming though Fiasco source code I checked out few weeks ago (the Doxygen online version is from 2005, out of date), I found 16 "Proc::preemption_point();" in the IPC path in the source file thread-ipc.cpp:

[sergio 19:41 ~/Desktop/FIASCO/tudos/kernel/fiasco/src/kern]$ grep Proc::preemption_point thread-ipc.cpp | wc -l 16

Which tudos/kernel/fiasco/src/drivers/processor.cpp defines as:

... static inline void preemption_point() { sti(); irq_chance(); [ NOP NOP ] cli(); } ...

My question is:

As far as I know, Fiasco is entirely preemptable. Then why sprinkling the IPC path with Enable IRQs/NOP NOP/Disable IRQs ?

Is there a document or a paper that discuss which parts of the kernel run with IRQs disabled / enabled ? Preemption disabled / enabled etc. ?

Thanks in advance,

Sergio