Software Engineering Lecture 4 Part 1: Synchronization and Security
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Questions and Answers

What is a race condition in software engineering?

  • A situation where multiple processes are writing to different locations in memory
  • A situation where two or more processes are reading or writing some shared data and the final result depends on timing (correct)
  • A situation where two processes are completely independent and do not interact with each other
  • A situation where a process gets stuck in an infinite loop

    • How can a race condition be avoided in software engineering?

  • By increasing the number of shared variables in the program
  • By allowing multiple processes to simultaneously access and modify the shared data
  • By introducing more complex dependencies between the processes
  • By ensuring that only one process at a time can manipulate the shared data (correct)

    • What is an example of a read-modify-write race condition?

  • Reading data from a file and writing it to another file concurrently
  • Sharing a single resource such as a printer among multiple processes
  • Simultaneously updating the balance of a bank account from multiple processes (correct)
  • Comparing two values and then updating a shared variable based on the comparison result

    • In the context of race conditions, what does 'Check-then-act' refer to?

    <p>Performing an action based on the result of a prior check, without any further synchronization</p> Signup and view all the answers

    What could happen in the train ticket booking example given if no synchronization is used?

    <p>Both passengers might end up booking the single available ticket</p> Signup and view all the answers

    How does synchronization help in avoiding race conditions?

    <p>By ensuring that any attempt to access shared data is coordinated and controlled</p> Signup and view all the answers

    What is the main issue described in the given code?

    <p>Race condition problem</p> Signup and view all the answers

    In the Train ticket booking example, what is the consequence of the race condition problem?

    <p>The available ticket count was reduced to -1</p> Signup and view all the answers

    What is the primary purpose of the 'Counter Race Condition Example'?

    <p>To demonstrate a race condition problem with the counter variable</p> Signup and view all the answers

    What is the common issue observed when running the 'Counter Race Condition Example' multiple times?

    <p>Different outputs are observed each time</p> Signup and view all the answers

    What is the role of 'Memory barriers' in hardware support for implementing critical section code?

    <p>To ensure immediate visibility of memory modifications to all processors</p> Signup and view all the answers

    What makes a memory model 'strongly ordered'?

    <p>Memory modifications of one processor are immediately visible to all other processors</p> Signup and view all the answers

    What is a potential consequence of using hardware that disables interrupts on uniprocessors?

    <p>Execution without preemption from currently running code</p> Signup and view all the answers

    What is the significance of 'atomic variables' in hardware support?

    <p>They ensure indivisible and atomic memory operations</p> Signup and view all the answers

    How does a computer architecture's memory model affect application programs?

    <p>It determines what memory guarantees it will provide to application programs</p> Signup and view all the answers

    What is the primary challenge faced by operating systems using hardware that disables interrupts on uniprocessors?

    <p>Scalability on multiprocessor systems</p> Signup and view all the answers

    What is the primary purpose of synchronization in the context of race conditions?

    <p>To ensure that only one process at a time can manipulate a variable</p> Signup and view all the answers

    What is the consequence of not using synchronization in the train ticket booking example?

    <p>Both passengers might end up booking the only available ticket</p> Signup and view all the answers

    What is the significance of 'Check-then-act' in the context of race conditions?

    <p>It checks the condition before taking action on shared data</p> Signup and view all the answers

    What is the main challenge when dealing with read-modify-write race conditions?

    <p>Handling situations where multiple processes are reading or writing shared data</p> Signup and view all the answers

    How does synchronization help in avoiding race conditions?

    <p>By ensuring that only one process at a time can manipulate a variable</p> Signup and view all the answers

    What is the consequence of a race condition in the context of shared data manipulation?

    <p>Unpredictable or incorrect results from shared data manipulation</p> Signup and view all the answers

    What is the consequence of the race condition problem in the Train ticket booking example?

    <p>Tickets count can never dip below 0 but it did</p> Signup and view all the answers

    What is the primary issue described in the given code?

    <p>Race condition problem in train ticket booking</p> Signup and view all the answers

    What is the primary challenge faced by operating systems using hardware that disables interrupts on uniprocessors?

    <p>Efficiency issues on multiprocessor systems</p> Signup and view all the answers

    What is a potential consequence of using hardware that disables interrupts on uniprocessors?

    <p>Efficiency issues on multiprocessor systems</p> Signup and view all the answers

    In the context of race conditions, what does 'Check-then-act' refer to?

    <p>A common pattern leading to concurrency problems</p> Signup and view all the answers

    What is the role of 'Memory barriers' in hardware support for implementing critical section code?

    <p>To provide immediate visibility of memory modifications to all processors</p> Signup and view all the answers

    How does a computer architecture's memory model affect application programs?

    <p>By determining what memory guarantees it will provide to an application program</p> Signup and view all the answers

    What makes a memory model 'strongly ordered'?

    <p>Immediate visibility of memory modifications to all processors</p> Signup and view all the answers

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