18-19-Synchronization using Semaphores

spatlou

All queries, discussions, updates and clarifications related to

Semaphores

should be posted here.

spatlou

nirmalpg124

semaphores are integer based synchronization mechanisms used to control access to a critical section of code in a program that could be accessed by several threads of a process.

these are wait & signal mechanisms. sem_wait & sem_post utilise & release a resource. Resource could be a variable or a section of code that involves a variable.

mohammaduvais143

Semaphore is a synchronization tool. It is implemented as a kernel data structure.

struct semaphore

{

semaphore var;

two atomic operations;

list of waiting processes;

spinlock;

}

It should be implemented where there is a shared resources are used.

suppose many process used some shared resource such as pipe.

The shared resource need to be protected by using semaphore.

nirmalpg124

semaphore could be used as a gate keeper for a concrete operation

entry & exit points of semaphore could be around any section of critical code

a ponter pointing to a memory allocated using malloc could be passed on to different processes and threads as an argument

semaphore are used for sharable resources while completion is used for shared resources they both are complementary to each other

macros are usually used for a data that is a constant that is an input to the process by the user while pointers are used to allocate memory

macros are used vigorously for data inputs by the user or a function defined with parameters

18-19-Synchronization using Semaphores

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