The following code example shows how an atomicity-violation bug can be fixed by_ 1 pthread_mutex_t proc_info_lock PTHREAD_MUTEX_INITIALIZER; Thread 1:: pthread_mutex_lock (sproc_info_lock); if (thd->proc_info) ( fputs (thd->proc_info, ...); 7. pthread_mutex_unlock (sproc_info_lock); 10 Thread 2:: pthread mutex_lock (&proc_info_lock); 12 thd->proc_info - NULL; pthread mutex_unlock (&proc_info_lock); 11 13 adding more thread parallelism avoiding deadlocks removing the shared variable adding locks around the shared variable references

Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
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The following code example shows how an atomicity-violation bug can be fixed by
pthread_mutex_t proc_info_lock = PTHREAD_MUTEX_INITIALIZER;
2
Thread 1::
pthread_mutex_lock (sproc_info_lock);
if (thd->proc_info) {
fputs (thd->proc_info, ...);
7
pthread_mutex_unlock (&proc_info_lock);
10
Thread 2::
pthread mutex_lock (&proc_info_lock);
thd->proc_info = NULL;
pthread_mutex_unlock (sproc_info_lock);
11
12
13
adding more thread parallelism
avoiding deadlocks
removing the shared variable
adding locks around the shared variable references
Transcribed Image Text:The following code example shows how an atomicity-violation bug can be fixed by pthread_mutex_t proc_info_lock = PTHREAD_MUTEX_INITIALIZER; 2 Thread 1:: pthread_mutex_lock (sproc_info_lock); if (thd->proc_info) { fputs (thd->proc_info, ...); 7 pthread_mutex_unlock (&proc_info_lock); 10 Thread 2:: pthread mutex_lock (&proc_info_lock); thd->proc_info = NULL; pthread_mutex_unlock (sproc_info_lock); 11 12 13 adding more thread parallelism avoiding deadlocks removing the shared variable adding locks around the shared variable references
The following code structures show how semaphores empty and full can be used to solve Producer/Consumer (Bounded-Buffer with n buffers) problem.
• The structure of the producer
• The structure of the consumer
while (true) {
while (true) {
wait (full)
/* produce an item /
wait (mutex),
--.
wait (empty);
/* remove an item from buffer */
wait (mutex) ;
...
poat (mutex) ;
/* add to the buffer */
poat (empty);
/* consume the item */
post (mutex);
post (full);
...
What is the purpose of the mutex in these two code structures?
O It indicates the number of empty slots in the buffer.
O It ensures that semaphores empty and full are both binary semaphores.
O It indicates the number of occupied slots in the buffer.
O It ensures mutual exclusion.
Transcribed Image Text:The following code structures show how semaphores empty and full can be used to solve Producer/Consumer (Bounded-Buffer with n buffers) problem. • The structure of the producer • The structure of the consumer while (true) { while (true) { wait (full) /* produce an item / wait (mutex), --. wait (empty); /* remove an item from buffer */ wait (mutex) ; ... poat (mutex) ; /* add to the buffer */ poat (empty); /* consume the item */ post (mutex); post (full); ... What is the purpose of the mutex in these two code structures? O It indicates the number of empty slots in the buffer. O It ensures that semaphores empty and full are both binary semaphores. O It indicates the number of occupied slots in the buffer. O It ensures mutual exclusion.
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