The kernel log levels are now numerically reversed so that more-verbose
levels can be added to the end. Replaced 'debug' with 'verbose', and
added new 'spam' level.
This bug has been making me tear my hair out for weeks. When creating
the idle thread for each CPU, we were previously sharing stack areas
with other CPUs' idle threads in an effort to save memory. However, this
caused stack corruption that was very hard to track down. The kernel
stacks are in a vm_area_guarded to better detect this exact kind of
issue, but splitting stacks like this skirts that protection. It's not
worth saving a few KiB per CPU.
When waking another thread, if that thread has a more urgent priority
than the current thread on the same CPU, send that CPU an IPI to tell it
to run its scheduler.
Related changes in this commit:
- Addition of the ipiSchedule isr (vector 0xe4) and its handler in
isr_handler().
- Change the APIC's send_ipi* functions to take an isr enum and not an
int for their vector parameter
- Thread TCBs now contain a pointer to their current CPU's cpu_data
structure
- Add the maybe_schedule() call to the scheduler, which sends the
schedule IPI to the given thread's CPU only when that CPU is running a
less-urgent thread.
- Move the locking of a run queue lock earlier in schedule() instead of
taking the lock in steal_work() and again in schedule().
The kernel/main.cpp and kernel/memory_bootstrap.cpp files had become
something of a junk drawer. This change cleans them up in the following
ways:
- Most CPU initialization has moved to cpu.cpp, allowing several
functions to be made static and removed from cpu.h
- Multi-core startup code has moved to the new smp.h and smp.cpp, and
ap_startup.s has been renamed smp.s to match.
- run_constructors() has moved to memory_bootstrap.cpp, and all the
functionality of that file has been hidden behind a new public
interface mem::initialize().
- load_init_server() has moved from memory_bootstrap.cpp to main.cpp
