scheduler_common.h is now meant for types, variables and functions used
by both core scheduler code and implementations of scheduler modes.
Functions like switch_thread() and update_thread_times() do not belong
there anymore.
We can't reliably set contemporary processors to an arbitrary frequency.
There are dependencies between cores and thechnologies like Turbo Boost
which may make actual frequency significantly different than the requested.
Moreover, it is the scheduler job to decide how much CPU performance is
needed and user shouldn't interfere with that.
In current state this driver is useless anyway. It's not MP safe.
The P-state values stored in hardcoded tables are only for processors
on which we can't use SpeedStep, because of lack of invariant TSC.
Proper driver should get P-states from ACPI, ensure that the CPU offers
invariant TSC and obviouslt be MP safe.
* Remove possibility to temporarily disable small task packing.
* When small task packing target gets overloaded continue packing
threads on another core, but avoid migrating the already packed
ones.
Scheduler still tends to needlessly migrate threads to another cores
when under heavier load, but it is now much better than before.
* pin idle threads to their specific CPUs
* allow scheduler to implement SMP_MSG_RESCHEDULE handler
* scheduler_set_thread_priority() reworked
* at reschedule: enqueue old thread after dequeueing the new one
* Thread::scheduler_lock protects thread state, priority, etc.
* sThreadCreationLock protects thread creation and removal and list of
threads in team.
* Team::signal_lock and Team::time_lock protect list of threads in team
as well.
* Scheduler uses its own internal locking.
* No need for the atomically changed variables to be declared as
volatile.
* Drop support for atomically getting and setting unaligned data.
* Introduce atomic_get_and_set[64]() which works the same as
atomic_set[64]() used to. atomic_set[64]() does not return the
previous value anymore.
