1Notes on the scheduler in sched.c:
2~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3
4  'sched.c' provides an very simplistic multi-threading scheduler.
5   See the example, function 'sched(...)', in the same file for its
6   API usage.
7
8   Until an exhaustive testing can be done, the implementation cannot
9   qualify as that of production quality. It works with the example
10   in 'sched.c', it may or may not work in other cases.
11
12
13Limitations:
14~~~~~~~~~~~~
15
16  - There are NO primitives for thread synchronization (locking,
17    notify etc).
18
19  - Only the GPRs and FPRs context is saved during a thread context
20    switch. Other registers on the PowerPC processor (60x, 7xx, 7xxx
21    etc) are NOT saved.
22
23  - The scheduler is NOT transparent to the user. The user
24    applications must invoke thread_yield() to allow other threads to
25    scheduler.
26
27  - There are NO priorities, and the scheduling policy is round-robin
28    based.
29
30  - There are NO capabilities to collect thread CPU usage, scheduler
31    stats, thread status etc.
32
33  - The semantics are somewhat based on those of pthreads, but NOT
34    the same.
35
36  - Only seven threads are allowed. These can be easily increased by
37    changing "#define MAX_THREADS" depending on the available memory.
38
39  - The stack size of each thread is 8KBytes. This can be easily
40    increased depending on the requirement and the available memory,
41    by increasing "#define STK_SIZE".
42
43  - Only one master/parent thread is allowed, and it cannot be
44    stopped or deleted. Any given thread is NOT allowed to stop or
45    delete itself.
46
47  - There NOT enough safety checks as are probably in the other
48    threads implementations.
49
50  - There is no parent-child relationship between threads. Only one
51    thread may thread_join, preferably the master/parent thread.
52
53(C) 2003 Arun Dharankar <ADharankar@ATTBI.Com>
54