109 lines
2.0 KiB
Plaintext
109 lines
2.0 KiB
Plaintext
Shared Variables: freelist, list-1, list-2: block
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Thread-1:
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var b: pointer to type block;
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while (true)
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{
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// wait for >1 block on freelist
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wait(sem_freelist_minus_1);
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// wait for element on freelist
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wait(sem_freelist);
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// mutual exclusion for freelist
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wait(mut_freelist);
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b := unlink(freelist);
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// mutual exclusion for freelist
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signal(mut_freelist);
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produce_information_in_block(b);
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// mutual exclusion for list1
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wait(mut_list1);
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link(b, list1);
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// mutual exclusion for list1
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signal(mut_list1);
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// signal new element on list1
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signal(sem_list1);
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}
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Thread-2:
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var x, y: pointer to type block;
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while (true)
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{
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// wait for element on list1
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wait(sem_list1);
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// mutual exclusion for list1
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wait(mut_list1);
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x := unlink(list-1);
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// mutual exclusion for list1
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signal(mut_list1);
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// wait for element on freelist
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wait(sem_freelist);
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// mutual exclusion for freelist
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wait(mut_freelist);
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y := unlink(freelist);
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// mutual exclusion for freelist
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signal(mut_freelist);
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use_block_x_to_produce_info_in_y(x, y);
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// mutual exclusion for freelist
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wait(mut_freelist);
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//* link(x, freelist);
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link(x, freelist);
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// mutual exclusion for freelist
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signal(mut_freelist);
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// signal new element on freelist
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signal(sem_freelist);
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// mutual exclusion for list2
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wait(mut_list2);
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link(y, list-2);
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// mutual exclusion for list2
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signal(mut_list2);
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// signal new element on list2
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signal(sem_list2);
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}
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Thread-3:
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var c: pointer to type block;
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while (true)
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{
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// wait for element on list2
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wait(sem_list2);
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// mutual exclusion for list2
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wait(mut_list2);
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c := unlink(list-2);
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// mutual exclusion for list2
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signal(mut_list2);
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consume_information_in_block(c);
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// mutual exclusion for freelist
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wait(mut_freelist);
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link(c, freelist);
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// mutual exclusion for freelist
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signal(mut_freelist);
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// signal Thread-1 to continue
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signal(sem_freelist_minus_1);
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// signal new element on freelist
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signal(sem_freelist);
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} |