Problem Scenario
This scenario presents particular complications:
- Process A makes a time-consuming system call. By "time-consuming", it is meant that the system needs to put Process A into a wait queue and can schedule another process for execution if one is ready-to-run. A common example is an I/O operation.
- While Process A is in this wait state, Process B tries to interact with access Process A, for example, send it a signal.
What should be the visible state of the context of Process A at the time of the access by Process B? In fact, it is in the middle of a system call, but ITS enforces the appearance that system calls are not visible to other processes (or even to the same process).
Read more about this topic: PCLSRing
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