- What happens when interrupts are disabled?
- Why spinlocks are not appropriate for single processor systems?
- What is mutual exclusion with busy waiting?
- What is interrupt disabling?
- What is enabling and disabling interrupts?
- Why interrupt must be disabled on all processors in a multiprocessor system to enforce mutual exclusion?
- Why mutual exclusion is required?
- What is interrupt in COA?
- What is enable and disable interrupts in 8086?
- What kinds of waiting are there in an operating system?
- What are the limitations of the interrupt disabling for mutual exclusion?
- What is critical section code?
What happens when interrupts are disabled?
The device responsible for an interrupt will not get any response while waiting – which is kind of a response anyway.
If it can’t wait, it might enter some error state that the CPU will see when it eventually comes around.
You will only get the interrupts you have explicitly enabled, so there should be no surprises..
Why spinlocks are not appropriate for single processor systems?
Spinlocks are not appropriate for single-processor systems because the condition that would break a process out of the spinlock can be obtained only by executing a different process.
What is mutual exclusion with busy waiting?
Before entering its critical region, a process calls enter_region, which does busy waiting until the lock is free; then it acquires the lock and returns. After the critical region the process calls leave_region, which stores a 0 in lock. … If a process cheats, the mutual exclusion will fail.
What is interrupt disabling?
By disabling interrupts the CPU will be unable to switch processes. This guarantees that the process can use the shared variable without another process accessing it. But, disabling interrupts, is a major undertaking. … At worst, the process may never enable interrupts, thus (effectively) crashing the computer.
What is enabling and disabling interrupts?
To enable means to allow interrupts at this time. Conversely, to disable means to postpone interrupts until a later time. On the ARM Cortex-M processor there is one interrupt enable bit for the entire interrupt system.
Why interrupt must be disabled on all processors in a multiprocessor system to enforce mutual exclusion?
Interrupts can break that because they cause control to be transferred from critical section to the interrupt handler. … Therefore, on a multiprocessor machine, disabling interrupts is not sufficient to achieve multiple exclusion. There also needs to be a way to prevent the other processors from accessing the resource.
Why mutual exclusion is required?
It is the requirement that a process can not enter its critical section while another concurrent process is currently present or executing in its critical section i.e only one process is allowed to execute the critical section at any given instance of time. Mutual exclusion in single computer system Vs.
What is interrupt in COA?
Interrupt is a signal emitted by hardware or software when a process or an event needs immediate attention. It alerts the processor to a high priority process requiring interruption of the current working process.
What is enable and disable interrupts in 8086?
For an interrupt to be disabled, its corresponding bit in the IMR must be 1. To be enabled, its bit must be 0. Interrupts can be enabled or disabled by the programmer by reading the IMR, setting or clearing the appropriate bits, then writing the new value back to the IMR. The IRR.
What kinds of waiting are there in an operating system?
Busy waiting: A process is waiting for an event to occur and it does so by executing instructions. Other types of waiting: A process is waiting for an event to occur in some waiting queue (e.g., I/O semaphore) and it does so without having the CPU assigned to it.
What are the limitations of the interrupt disabling for mutual exclusion?
Interrupt disabling guarantees mutual exclusion. The disadvantage of this is that efficiency of execution could be noticeably downgraded. This approach also wouldn’t work in a microprocessor architecture. What are the ways in which the requirements for mutual exclusion can be satisfied?
What is critical section code?
The critical section is a code segment where the shared variables can be accessed. An atomic action is required in a critical section i.e. only one process can execute in its critical section at a time. … It acquires the resources needed for execution by the process.