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54 lines
1.8 KiB
Text
54 lines
1.8 KiB
Text
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Notes on the scheduler in sched.c:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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'sched.c' provides an very simplistic multi-threading scheduler.
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See the example, function 'sched(...)', in the same file for its
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API usage.
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Until an exhaustive testing can be done, the implementation cannot
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qualify as that of production quality. It works with the example
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in 'sched.c', it may or may not work in other cases.
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Limitations:
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~~~~~~~~~~~~
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- There are NO primitives for thread synchronization (locking,
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notify etc).
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- Only the GPRs and FPRs context is saved during a thread context
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switch. Other registers on the PowerPC processor (60x, 7xx, 7xxx
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etc) are NOT saved.
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- The scheduler is NOT transparent to the user. The user
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applications must invoke thread_yield() to allow other threads to
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scheduler.
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- There are NO priorities, and the scheduling policy is round-robin
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based.
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- There are NO capabilities to collect thread CPU usage, scheduler
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stats, thread status etc.
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- The semantics are somewhat based on those of pthreads, but NOT
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the same.
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- Only seven threads are allowed. These can be easily increased by
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changing "#define MAX_THREADS" depending on the available memory.
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- The stack size of each thread is 8KBytes. This can be easily
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increased depending on the requirement and the available memory,
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by increasing "#define STK_SIZE".
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- Only one master/parent thread is allowed, and it cannot be
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stopped or deleted. Any given thread is NOT allowed to stop or
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delete itself.
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- There NOT enough safety checks as are probably in the other
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threads implementations.
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- There is no parent-child relationship between threads. Only one
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thread may thread_join, preferably the master/parent thread.
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(C) 2003 Arun Dharankar <ADharankar@ATTBI.Com>
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