- this patch only renames schedcheck() to switch_to_user(),
cycles_accounting_stop() to context_stop() and restart() to
+restore_user_context()
- the motivation is that since the introduction of schedcheck() it has
been abused for many things. It deserves a better name. It should
express the fact that from the moment we call the function we are in
the process of switching to user.
- cycles_accounting_stop() was originally a single purpose function.
As this function is called at were convenient places it is used in
for other things too, e.g. (un)locking the kernel. Thus it deserves
a better name too.
- using the old name, restart() does not call schedcheck(), however
calls to restart are replaced by calls to schedcheck()
[switch_to_user] and it calls restart() [restore_user_context]
- When the cpu halts, the interrupts are enable so the cpu may be
woken up. When the interrupt handler returns but another interrupt
is available it is also serviced immediately. This is not a problem
per-se. It only slightly breaks time accounting as idle accounted is
for the kernel time in the interrupt handler.
- As the big kernel lock is lock/unlocked in the smp branch in the
time acounting functions as they are called exactly at the places
we need to take the lock) this leads to a deadlock.
- we make sure that once the interrupt handler returns from the nested
trap, the interrupts are disabled. This means that only one
interrupt is serviced after idle is interrupted.
- this requires the loop in apic timer calibration to keep reenabling
the interrupts. I admit it is a little bit hackish (one line),
however, this code is a stupid corner case at the boot time.
Hopefully it does not matter too much.
Move archtypes.h to include/ dir, since several servers require it. Move
fpu.h and stackframe.h to arch-specific header directory. Make source
files and makefiles aware of the new header locations.
- as thre are still KERNEL and IDLE entries, time accounting for
kernel and idle time works the same as for any other process
- everytime we stop accounting for the currently running process,
kernel or idle, we read the TSC counter and increment the p_cycles
entry.
- the process cycles inherently include some of the kernel cycles as
we can stop accounting for the process only after we save its
context and we start accounting just before we restore its context
- this assumes that the system does not scale the CPU frequency which
will be true for ... long time ;-)
- local APIC timer used as the source of time
- PIC is still used as the hw interrupt controller as we don't have
enough info without ACPI or MPS to set up IO APICs
- remapping of APIC when switching paging on, uses the new mechanism
to tell VM what phys areas to map in kernel's virtual space
- one more step to SMP
based on code by Arun C.
