Bounded Buffer Problem in Operating System

January 20, 2023

About Bounded Buffer Problem in OS

On this page, we will learn the concepts of Bounded Buffer problem in operating system.
Bounded buffer problem in operating system refers to the general case of the producer – consumer problem wherein the access is
controlled to a shared group of buffers of limited size.

Bounded Buffer Problem in Operating System using Semaphores

In Bounded Buffer Problem there are three entities storage buffer slots, consumer and producer. The producer tries to store data in the storage slots while the consumer tries to remove the data from the buffer storage.

It is one of the most important process synchronizing problem let us understand more about the same.

Priority Scheduling

CPU Scheduling

FCFS Scheduling

Preemptive Scheduling

Problem

The bounded buffer problem uses Semaphore. Please read more about Semaphores here before proceeding with this post here.

We need to make sure that the access to data buffer is only either to producer or consumer, i.e. when producer is placing the item in the buffer the consumer shouldn’t consume.

We do that via three entities –

Mutex mutex – used to lock and release critical section
empty – Keeps tab on number empty slots in the buffer at any given time
- Initialised as n as all slots are empty.
full – Keeps tab on number of entities in buffer at any given time.
- Initialised as 0

Readers Writer Wait and Signal Implementation

wait(Semaphore s)
{
  while(s == 0);
  s = s-1;
}

signal(Semaphore s)
{
  s = s+1;
}

What happened above: semicolon after while , which results in the while loop getting executed again again. Until S value is non-zero.

Producer Buffer Solution

do
  {
    // wait until empty > 0 and then decrement 'empty'
    // that is there must be atleast 1 empty slot
    
    wait (empty);
    
    // acquire the lock, so consumer can't enter
    
    wait (mutex);

    /* perform the insert operation in a slot */

    // release lock
    
    signal (mutex);
    
    // increment 'full'
    
    signal (full);
  }
while (TRUE)

Consumer Buffer Solution

do 
{
    // wait until full > 0 and then decrement 'full'
    // should be atleast 1 full slot in buffer
    
    wait(full);
    
    // acquire the lock
   
    wait(mutex);  
    
    /* perform the remove operation in a slot */ 
    
    // release the lock
    
    signal(mutex); 
    
    // increment 'empty'
    
    signal(empty); 
} 
while(TRUE);

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