Access primitives
Last updated
Last updated
Requirements that should be observed in accessing a critical section:
Effective mutual exclusion – access to the critical sections associated with the same resource, or shared area, can only be allowed to one process at a time, among all processes that compete for access.
Independence on the number of intervening processes or on their relative speed of execution.
A process outside its critical section cannot prevent another process from entering its own critical section.
No starvation – a process requiring access to its critical section should not have to wait indefinitely.
Length of stay inside a critical section should be necessarily finite.
In general, a memory location is used to control access to the critical section.
it works as a binary flag.
Two types of solutions: software solutions and hardware solutions.
software solutions – solutions that are based on the typical instructions used to access memory location.
read and write are done by different instructions.
interruption can occur between read and write.
hardware solutions – solutions that are based on special instructions to access the memory location.
these instructions allow to read and then write a memory location in an atomic (uninterruptible) way.
