144 lines
5.9 KiB
ReStructuredText
144 lines
5.9 KiB
ReStructuredText
.. _dining-philosophers-sample:
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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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.. zephyr-app-commands::
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:zephyr-app: samples/philosophers
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:host-os: unix
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:board: qemu_x86
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:goals: run
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:compact:
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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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Exit QEMU by pressing :kbd:`CTRL+A` :kbd:`x`.
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Debug Threads
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*************
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The philosophers sample by default enables :kconfig:option:`CONFIG_DEBUG_THREAD_INFO`.
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This allows tools like OpenOCD and J-link to inspect thread data using
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``info threads``.
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.. zephyr-app-commands::
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:zephyr-app: samples/philosophers
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:host-os: unix
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:board: <board_name>
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:goals: debug
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:compact:
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OpenOCD Sample Output
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=====================
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.. code-block:: console
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Thread 1 received signal SIGINT, Interrupt.
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[Switching to Thread 537003160]
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arch_cpu_idle () at zephyr/mainline/zephyr/arch/arm/core/aarch32/cpu_idle.S:107
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107 cpsie i
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(gdb) i threads
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Id Target Id Frame
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* 1 Thread 537003160 (Name: idle 00, prio:40,useropts:1) arch_cpu_idle () at zephyr/mainline/zephyr/arch/arm/core/aarch32/cpu_idle.S:107
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Info : Getting thread 537002984 reg list
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2 Thread 537002984 (Name: Philosopher 5, prio:-2,useropts:4) 0x08001404 in arch_irq_unlock (key=0) at zephyr/mainline/zephyr/include/arch/arm/aarch32/asm_inline_gcc.h:95
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Info : Getting thread 537002808 reg list
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3 Thread 537002808 (Name: Philosopher 4, prio:-1,useropts:4) 0x08001404 in arch_irq_unlock (key=0) at zephyr/mainline/zephyr/include/arch/arm/aarch32/asm_inline_gcc.h:95
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Info : Getting thread 537002632 reg list
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4 Thread 537002632 (Name: Philosopher 3, prio:0,useropts:4) 0x08001404 in arch_irq_unlock (key=0) at zephyr/mainline/zephyr/include/arch/arm/aarch32/asm_inline_gcc.h:95
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Info : Getting thread 537002456 reg list
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5 Thread 537002456 (Name: Philosopher 2, prio:1,useropts:4) 0x08001404 in arch_irq_unlock (key=0) at zephyr/mainline/zephyr/include/arch/arm/aarch32/asm_inline_gcc.h:95
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Info : Getting thread 537002280 reg list
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6 Thread 537002280 (Name: Philosopher 1, prio:2,useropts:4) 0x08001404 in arch_irq_unlock (key=0) at zephyr/mainline/zephyr/include/arch/arm/aarch32/asm_inline_gcc.h:95
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Info : Getting thread 537002104 reg list
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7 Thread 537002104 (Name: Philosopher 0, prio:3,useropts:4) 0x08001404 in arch_irq_unlock (key=0) at zephyr/mainline/zephyr/include/arch/arm/aarch32/asm_inline_gcc.h:95
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.. code-block:: console
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Philosopher 0 [P: 3] STARVING
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Philosopher 1 [P: 2] HOLDING ONE FORK
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Philosopher 2 [P: 1] EATING [ 400 ms ]
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Philosopher 3 [P: 0] THINKING [ 525 ms ]
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Philosopher 4 [C:-1] HOLDING ONE FORK
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Philosopher 5 [C:-2] EATING [ 625 ms ]
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J-Link Sample Output
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====================
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.. code-block:: console
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Thread 2 received signal SIGTRAP, Trace/breakpoint trap.
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[Switching to Thread 537920592]
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arch_cpu_idle () at zephyr/mainline/zephyr/arch/arm/core/aarch32/cpu_idle.S:107
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107 cpsie i
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(gdb) i threads
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Id Target Id Frame
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* 2 Thread 537920592 (idle 00 UNKNOWN PRIO 40) arch_cpu_idle () at zephyr/mainline/zephyr/arch/arm/core/aarch32/cpu_idle.S:107
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3 Thread 537919536 (Philosopher 0 PENDING PRIO 3) arch_swap (key=0) at zephyr/mainline/zephyr/arch/arm/core/aarch32/swap.c:53
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4 Thread 537919712 (Philosopher 1 SUSPENDED PRIO 2) arch_swap (key=key@entry=0) at zephyr/mainline/zephyr/arch/arm/core/aarch32/swap.c:53
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5 Thread 537919888 (Philosopher 2 SUSPENDED PRIO 1) arch_swap (key=key@entry=0) at zephyr/mainline/zephyr/arch/arm/core/aarch32/swap.c:53
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6 Thread 537920064 (Philosopher 3 SUSPENDED PRIO 0) arch_swap (key=key@entry=0) at zephyr/mainline/zephyr/arch/arm/core/aarch32/swap.c:53
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7 Thread 537920240 (Philosopher 4 PENDING PRIO 255) arch_swap (key=0) at zephyr/mainline/zephyr/arch/arm/core/aarch32/swap.c:53
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8 Thread 537920416 (Philosopher 5 SUSPENDED PRIO 254) arch_swap (key=key@entry=0) at zephyr/mainline/zephyr/arch/arm/core/aarch32/swap.c:53
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.. code-block:: console
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Philosopher 0 [P: 3] STARVING
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Philosopher 1 [P: 2] EATING [ 475 ms ]
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Philosopher 2 [P: 1] THINKING [ 700 ms ]
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Philosopher 3 [P: 0] THINKING [ 525 ms ]
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Philosopher 4 [C:-1] HOLDING ONE FORK
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Philosopher 5 [C:-2] EATING [ 625 ms ]
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