62 lines
1.8 KiB
ReStructuredText
62 lines
1.8 KiB
ReStructuredText
Dining Philosophers
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###################
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Overview
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********
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An implementation of a solution to the Dining Philosophers problem (a classic
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multi-thread synchronization problem). This particular implementation
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demonstrates the usage of multiple preemptible and cooperative threads of
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differing priorities, as well as dynamic mutexes and thread sleeping.
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The philosopher always tries to get the lowest fork first (f1 then f2). When
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done, he will give back the forks in the reverse order (f2 then f1). If he
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gets two forks, he is EATING. Otherwise, he is THINKING. Transitional states
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are shown as well, such as STARVING when the philosopher is hungry but the
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forks are not available, and HOLDING ONE FORK when a philosopher is waiting
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for the second fork to be available.
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Each Philosopher will randomly alternate between the EATING and THINKING state.
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It is possible to run the demo in coop-only or preempt-only mode. To achieve
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this, set these values for CONFIG_NUM_COOP_PRIORITIES and
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CONFIG_NUM_PREEMPT_PRIORITIES in prj.conf:
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preempt-only:
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CONFIG_NUM_PREEMPT_PRIORITIES 6
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CONFIG_NUM_COOP_PRIORITIES 0
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coop-only:
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CONFIG_NUM_PREEMPT_PRIORITIES 0
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CONFIG_NUM_COOP_PRIORITIES 6
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In these cases, the philosopher threads will run with priorities 0 to 5
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(preempt-only) and -7 to -2 (coop-only).
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Building and Running
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********************
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This project outputs to the console. It can be built and executed
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on QEMU as follows:
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.. code-block:: console
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$ cd samples/philosophers
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$ make run
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Sample Output
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=============
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.. code-block:: console
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Philosopher 0 [P: 3] HOLDING ONE FORK
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Philosopher 1 [P: 2] HOLDING ONE FORK
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Philosopher 2 [P: 1] EATING [ 1900 ms ]
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Philosopher 3 [P: 0] THINKING [ 2500 ms ]
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Philosopher 4 [C:-1] THINKING [ 2200 ms ]
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Philosopher 5 [C:-2] THINKING [ 1700 ms ]
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