Process Synchronization - Monitors
- 2. One of the ways to achieve Process synchronization. The monitor is supported by programming languages to achieve mutual exclusion between processes. It is the collection of condition variables and procedures combined together in a special kind of module or a package. The processes running outside the monitor can’t access the internal variable of the monitor but can call procedures of the monitor. Only one process at a time can execute code inside monitors. 9/29/2021 2 Dr.M.Karthika/AP/MTNC
- 3. 1. Inside the monitors, we can only execute one process at a time. 2. Monitors are the group of procedures, and condition variables that are merged together in a special type of module. 3. If the process is running outside the monitor, then it cannot access the monitor’s internal variable. But a process can call the procedures of the monitor. 4. Monitors offer high-level of synchronization 5. Monitors were derived to simplify the complexity of synchronization problems. 6. There is only one process that can be active at a time inside the monitor. 9/29/2021 Dr.M.Karthika/AP/MTNC 3
- 5. Two different operations are performed on the condition variables of the monitor. Wait. signal. let say we have 2 condition variables condition x, y; // Declaring variable 9/29/2021 5 Dr.M.Karthika/AP/MTNC
- 6. x.wait() : Process performing wait operation on any condition variable are suspended. The suspended processes are placed in block queue of that condition variable. Note: Each condition variable has its unique block queue. 9/29/2021 6 Dr.M.Karthika/AP/MTNC
- 7. x.signal(): When a process performs signal operation on condition variable, one of the blocked processes is given chance. If (x block queue empty) // Ignore signal else // Resume a process from block queue. 9/29/2021 7 Dr.M.Karthika/AP/MTNC
- 8. Advantages of Monitor: Monitors have the advantage of making parallel programming easier and less error prone than using techniques such as semaphore. Disadvantages of Monitor: Monitors have to be implemented as part of the programming language . The compiler must generate code for them. This gives the compiler the additional burden of having to know what operating system facilities are available to control access to critical sections in concurrent processes. 9/29/2021 8 Dr.M.Karthika/AP/MTNC