- switch_address_space() implements a switch of the user address space
for the destination process
- this makes memory of this process easily accessible, e.g. a pointer
valid in the userspace can be used with a little complexity to
access the process's memory
- the switch does not happed only just before we return to userspace,
however, it happens right after we know which process we are going
to schedule. This happens before we start processing the misc flags
of this process so its memory is available
- if the process becomes not runnable while processing the mics flags
we pick a new process and we switch the address space again which
introduces possibly a little bit more overhead, however, it is
hopefully hidden by reducing the overheads when we actually access
the memory
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