Consumer Producer Problem
Producer Consumer Problem using Semaphores in Operating System
The producer-consumer problem is a classic multiprocess synchronization problem. In the Producer-Consumer problem there is a producer, a producer produces some items, and a consumer who consumes the items produced by the producer. Producers and consumers share the same fixed-size memory buffer.
Producer Consumer Problem using Semaphores
Producer consumer problem is one classic example of mutual exclusion, process synchronisation using semaphores. It basically synchronises data production and consumption happening simultaneously in a system where there is fixed amount of storage size. The system has the following –- Producer
- Consumer
- Storage bound of size n
Process of Producer Consumer
The processes is synchronised via a mutex which provides mutual mutual exclusion in the critical section area. There is unit called as empty which defines the number of empty slots in the storage. There is unit called as full which defines the number of full storage slots in the system.
The number of storage slots are initialised as n, the number of empty slots are initialised as n since all slots are empty at the starting similarly the full unit is initialised as 0 as there is no data initially.
It is important to understand wait and signal first from the image above to understand how the problem works.
Producer Consumer Signal and Wait
wait(Semaphore s)
{
while(s == 0);
s = s-1;
}
signal(Semaphore s)
{
s = s+1;
}
Producer
do
{
// produce an item
// the producer can only produce if there is atleast 1 empty slot
// thus empty must be >0 and then it also decrements the value
wait (empty);
// access to critical section is blocked for consumer section
wait (mutex);
// place in buffer
// access to critical section is released
signal (mutex);
// value of full is incremented
signal (full);
}
while (true)
Consumer
do
{
// consumer should wait until there is atleast one item in storage
// full value should be greater than 0 and then decremented
wait (full);
// access to critical section is blocked for producer section
wait (mutex);
// remove item from buffer
// access to critical section is released for producer section
signal (mutex);
// value of empty is incremented as item was consumer
signal (empty);
// consumes item
}
while (true)
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