Consider the following code relating to condition variables from your textbook: and 6 7 . 9 10 18 19 20 21 22 void thr_exit() ( Pthread_mutex lock (6m); done = 1; Pthread_cond_signal(&c); Pthread_mutex_unlock (6m); void thr_join () { Pthread_mutex_lock (6m); while (done == 0) Pthread_cond_wait (&c, &m); Pthread_mutex_unlock (6m); Note the presence of a • variable (done), • a mutex (m), • a condition variable (c), and • a while loop all of which are necessary to get this to work correctly. a. Please explain why we need the variable (i.e., what might occur or what additional code might be needed if we omit the variable) b. Please explain why we need the mutex (same comment) c. Please explain why we need the condition variable d. Please explain why we need a while loop instead of an if statement Please keep your answers short and to the point. You might wish to show a schedule that might occur without each of these, should that be the best way to explain it concisely.

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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. This should have a specific answer (i.e.,tell me a specific case that might happen). 

Consider the following code relating to condition variables from
your textbook:
and
s void thr_exit () {
7
9
18
19
20
21
22
Pthread_mutex lock (6m);
done = 1;
Pthread_cond_signal (&c);
Pthread_mutex unlock (6m);
void thr_join () {
Pthread_mutex_lock (&m);
while (done == 0)
Pthread_cond_wait (&c, &m);
Pthread_mutex_unlock (6m);
Note the presence of a
variable (done),
• a mutex (m),
• a condition variable (c), and
• a while loop
all of which are necessary to get this to work correctly.
a. Please explain why we need the variable (i.e., what might occur
or what additional code might be needed if we omit the variable)
b. Please explain why we need the mutex (same comment)
c. Please explain why we need the condition variable
d. Please explain why we need a while loop instead of an if
statement
Please keep your answers short and to the point. You might wish to
show a schedule that might occur without each of these, should
that be the best way to explain it concisely.
Transcribed Image Text:Consider the following code relating to condition variables from your textbook: and s void thr_exit () { 7 9 18 19 20 21 22 Pthread_mutex lock (6m); done = 1; Pthread_cond_signal (&c); Pthread_mutex unlock (6m); void thr_join () { Pthread_mutex_lock (&m); while (done == 0) Pthread_cond_wait (&c, &m); Pthread_mutex_unlock (6m); Note the presence of a variable (done), • a mutex (m), • a condition variable (c), and • a while loop all of which are necessary to get this to work correctly. a. Please explain why we need the variable (i.e., what might occur or what additional code might be needed if we omit the variable) b. Please explain why we need the mutex (same comment) c. Please explain why we need the condition variable d. Please explain why we need a while loop instead of an if statement Please keep your answers short and to the point. You might wish to show a schedule that might occur without each of these, should that be the best way to explain it concisely.
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