In-class notes for 09/25/2019 (CS 273 (OS), Fall 2019)

In-class notes for 09/25/2019

CS 273 (OS), Fall 2019

HW5 assignment, first stages of developing shell project
- Note: Lab 2 is the first step, so you can submit something on time.
- The other steps are much shorter than Lab 2!
CI feedback on commits
- Merge commit...
Shell project
Readings - see Syllabus
- Please do readings on time (though we got behind in class recently)
- Bring questions to class, or ask RAB by email so they can be answered in class

Threads and race conditions

Threads - multiple execution paths within a single process.
- Differences between a process and a thread
- Examples of code with threads
Race conditions - correct behavior of the computation depends on timing
- Demonstration - OpenMP program trap_omp.c.
  - The program correctly computes the area under one loop of the sin(x) curve (mathematical answer 2) for one thread in the command
```
~rab/os/egs/trap_omp 1
```
  - What happens when there are more than one thread?
```
~rab/os/egs/trap_omp 2
~rab/os/egs/trap_omp 4
```
    Explanation...
Dining philosophers example
- In-class acted algorithms (3)
- sleep() and wakeup() functions?
  - sleep() blocks the calling thread/process
  - wakeup() unblocks another thread/process
Locating race conditions in code

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