in CompareAndSwap entry section

in CompareAndSwap exit section

Simplest is mutex lock, boolean variable indicating if lock is available or not

Calls to acquire () and release () can’t be atomi

in Mutex Locks Spinlocks is ideal for single-CPU as it is wasteful of CPU cycles that other process might be able to use productively

semaphore S is an integer variable that can only be modified via two interruptible operations: wait () and signal ()

in semaphore wait function the value of the integer is

in semaphore signal function the value of the integer is

integer value can range only between 0 and 1

a mutex lock

The main issue with semaphores is the busy loop in the signal() which eats CPU cycles without
accomplishing anything useful

semaphore implementation with no busy waiting there’s an associated waiting queue

remove one of processes in the waiting queue and place it in the ready queue

place the process invoking the operation on the appropriate waiting queue

two or more processes are waiting indefinitely for an event that can be caused by only one of the
waiting processes

indefinite blocking

A process may never be removed from the semaphore queue in which it is suspended

Mutual exclusion can be provided by the....