Definition: Bounded waiting refers to a process P_i that keeps waiting forever to enter critical section (CS) while other processes P_j keep entering CS although P_i has shown interest to enter CS.
Now, I understand why lock variable mechanism is not bounded waiting because if a process entered a non-critical section, then another process might come and take CS, so a process might starve.
Algorithm:
NCS (Non-critical Section)
DISABLE INTERRUPTS
CS
ENABLE INTERRUPTS
NCS
Edit: no more details are given about schedulers, etc. The question is to get a glance whether this satisfies bounded waiting or not.
Question: can you please explain why disabled interrupts synchronization mechanism satisfies bounded waiting please (a process can not starve to enter CS as in lock variable mechanism)?
Your question has two contexts to consider:
No,No
As soon as P_i releases the CS, the release mechanism can accept P_j, thus starvation is averted.
No,Yes
Despite P_j's desire, once interrupts are released, the scheduler could be invoked, and decide that P_j is not to be executed next, so in at least a pathological case, could spend forever trying to enter the CS while others are selected.
Yes,No
As soon as P_i release the interrupt, any pending interrupts will execute immediately. If they are to enter the CS, they will first (otherwise the system has halted [*]), so with the right timing a set of interrupts could keep P_j starved forever.
Yes,Yes Here, the starvation could happen for either of the reasons No,Yes or Yes,No.
[*] - Interrupts have no a-priori way of deferring work, so any resources required to complete the interrupt handler must be available when the handler runs. The handlers context is effectively nested; and a nested context cannot wait for the completion of its superior context.