Operating Systems 2026F: Tutorial 6 - Revision history

Soma: /* A: Getting Started */

2026-11-08T15:59:26Z

A: Getting Started

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	# Run all four programs with the same arguments of your choice. Do this a few times. Do they behave the same way? Do you notice any differences?		# Run all four programs with the same arguments of your choice. Do this a few times. Do they behave the same way? Do you notice any differences?
	# Repeat the above experiment, this time running each program under strace (with the -f flag to trace children too). Do you notice any difference in the system calls each program makes?		# Repeat the above experiment, this time running each program under strace (with the -f flag to trace children too). Do you notice any difference in the system calls each program makes?
	# Run <tt>sudo ./follow.bt</tt> and observe its output. What does it tell you about the executing programs? Does it output the same things for all of the programs?		# Run <tt>sudo ./[[#follow.bt\|follow.bt]]</tt> and observe its output. What does it tell you about the executing programs? Does it output the same things for all of the programs?

	==B: Producer/Consumer with Pipes==		==B: Producer/Consumer with Pipes==

Soma: /* Code */

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Code

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	}		}
	</syntaxhighlight>		</syntaxhighlight>


	===follow.bt===		===follow.bt===

Soma: /* Code */

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Code

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          return -1;
+}
 </syntaxhighlight>

Soma: /* C: Producer/Consumer with Shared Memory */

2026-11-08T15:54:54Z

C: Producer/Consumer with Shared Memory

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	<ol>		<ol>
	<li>Examine the source code of 3000pc-rendezvous. Explain the following:		<li>Examine the source code of [[#3000pc-rendezvous.c\|3000pc-rendezvous]]. Explain the following:
	<ol style="list-style-type:lower-alpha">		<ol style="list-style-type:lower-alpha">
	<li>What are a few ways that 3000pc-rendezvous is different from 3000pc-fifo?</li>		<li>What are a few ways that 3000pc-rendezvous is different from 3000pc-fifo?</li>
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	<li>Another student tells you that the difference between processes and threads is that processes never share memory, while threads do. Is this statement correct or incorrect? How can the behavior of 3000pc-rendezvous help justify your answer?</li>		<li>Another student tells you that the difference between processes and threads is that processes never share memory, while threads do. Is this statement correct or incorrect? How can the behavior of 3000pc-rendezvous help justify your answer?</li>
	<li>Change the calls to pthread_mutexattr_setpshared and pthread_condattr_setpshared to take 0 instead of 1. How does the behavior or 3000pc-rendezvous change? Does anything break? Demonstrate this using your answers to question 2 and question 3.</li>		<li>Change the calls to pthread_mutexattr_setpshared and pthread_condattr_setpshared to take 0 instead of 1. How does the behavior or 3000pc-rendezvous change? Does anything break? Demonstrate this using your answers to question 2 and question 3.</li>
	<li>3000pc-rendezvous can deadlock when run for long enough, with no sleeps and with output not going to the terminal. 3000pc-rendezvous-timeout should not deadlock, but it may pause sometimes. What is the difference between these two programs? Why would this difference affect their tendency to deadlock?		<li>3000pc-rendezvous can deadlock when run for long enough, with no sleeps and with output not going to the terminal. [[#3000pc-rendezvous-timeout.c\|3000pc-rendezvous-timeout]] should not deadlock, but it may pause sometimes. What is the difference between these two programs? Why would this difference affect their tendency to deadlock? (Hint: <tt>follow.bt</tt> can help you tell whether it is deadlocked.)
	<li>Benchmark the programs using the time command. For example, run 3000fifo as follows:<br /><br />		<li>Benchmark the programs using the time command. For example, run 3000fifo as follows:<br /><br />
	<tt>  time (./3000pc-fifo 100000 0 0 > fifo-output.log)</tt><br /><br />		<tt>  time (./3000pc-fifo 100000 0 0 > fifo-output.log)</tt><br /><br />

Soma: /* B: Producer/Consumer with Pipes */

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B: Producer/Consumer with Pipes

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	<li>Note that [[#3000pc-fifo-random.c\|3000pc-fifo-random]] uses /dev/urandom to pick its words instead of the C library's random functions. How do these two methods differ? You may wish to look at man urandom(4).</li>		<li>Note that [[#3000pc-fifo-random.c\|3000pc-fifo-random]] uses /dev/urandom to pick its words instead of the C library's random functions. How do these two methods differ? You may wish to look at man urandom(4).</li>
	<li>What do you think would happen if you had multiple producers and multiple consumers in 3000pc-fifo? Would things break or work normally?</li>		<li>What do you think would happen if you had multiple producers and multiple consumers in 3000pc-fifo? Would things break or work normally?</li>
	<li>(Advanced) Implement multiple producers and consumers in 3000pc-fifo. Compare your results with your answer to question 4.</li>		<li>(Advanced) Implement multiple producers and consumers in 3000pc-fifo. Compare your results with your answer to question C.9.</li>
	</ol>		</ol>

Soma: /* B: Producer/Consumer with Pipes */

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B: Producer/Consumer with Pipes

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	<li>Replace the call to srandom(time(NULL)) on line 169 with srandom(42). What differences do you notice in 3000pc-fifo's behavior?</li>		<li>Replace the call to srandom(time(NULL)) on line 169 with srandom(42). What differences do you notice in 3000pc-fifo's behavior?</li>
	<li>What descriptors are opened by 3000pc-fifo? What are they for and what files do the point to? How did you find this information? Hint: Try checking in /proc.</li>		<li>What descriptors are opened by 3000pc-fifo? What are they for and what files do the point to? How did you find this information? Hint: Try checking in /proc.</li>
	<li>Note that 3000pc-fifo-random uses /dev/urandom to pick its words instead of the C library's random functions. How do these two methods differ? You may wish to look at man urandom(4).</li>		<li>Note that [[#3000pc-fifo-random.c\|3000pc-fifo-random]] uses /dev/urandom to pick its words instead of the C library's random functions. How do these two methods differ? You may wish to look at man urandom(4).</li>
	<li>What do you think would happen if you had multiple producers and multiple consumers in 3000pc-fifo? Would things break or work normally?</li>		<li>What do you think would happen if you had multiple producers and multiple consumers in 3000pc-fifo? Would things break or work normally?</li>
	<li>(Advanced) Implement multiple producers and consumers in 3000pc-fifo. Compare your results with your answer to question 4.</li>		<li>(Advanced) Implement multiple producers and consumers in 3000pc-fifo. Compare your results with your answer to question 4.</li>

Soma: /* B: Producer/Consumer with Pipes */

2026-11-08T15:50:39Z

B: Producer/Consumer with Pipes

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	<ol>		<ol>
	<li>Examine the source code of [[#3000pc-fifo\|3000pc-fifo]]. Explain the following:		<li>Examine the source code of [[#3000pc-fifo.c\|3000pc-fifo]]. Explain the following:
	<ol style="list-style-type:lower-alpha">		<ol style="list-style-type:lower-alpha">
	<li>What does the call to pipe(pipefd) on line 192 do? Hint: Look at the manpage for pipe(2)</li>		<li>What does the call to pipe(pipefd) on line 192 do? Hint: Look at the manpage for pipe(2)</li>

Soma: /* B: Producer/Consumer with Pipes */

2026-11-08T15:49:36Z

B: Producer/Consumer with Pipes

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	<ol>		<ol>
	<li>Examine the source code of 3000pc-fifo. Explain the following:		<li>Examine the source code of [[#3000pc-fifo\|3000pc-fifo]]. Explain the following:
	<ol style="list-style-type:lower-alpha">		<ol style="list-style-type:lower-alpha">
	<li>What does the call to pipe(pipefd) on line 192 do? Hint: Look at the manpage for pipe(2)</li>		<li>What does the call to pipe(pipefd) on line 192 do? Hint: Look at the manpage for pipe(2)</li>

Soma: /* C: Producer/Consumer with Shared Memory */

2026-11-08T15:48:45Z

C: Producer/Consumer with Shared Memory

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	<ol style="list-style-type:lower-alpha">		<ol style="list-style-type:lower-alpha">
	<li>What are a few ways that 3000pc-rendezvous is different from 3000pc-fifo?</li>		<li>What are a few ways that 3000pc-rendezvous is different from 3000pc-fifo?</li>
	<li>What does the call to mmap on line ~~335~~ do? How did you figure this out?</li>		<li>What does the call to mmap on line 319 do? How did you figure this out?</li>
	<li>How does the producer notify the consumer that the queue is no longer empty?</li>		<li>How does the producer notify the consumer that the queue is no longer empty?</li>
	<li>How does the consumer notify the producer that the queue is no longer full?</li>		<li>How does the consumer notify the producer that the queue is no longer full?</li>

Soma: /* Code */

2026-11-08T15:45:17Z

Code

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