![]() ![]() As a result, the values output by the child at line X are 0, -1, -4, -9, -16. ![]() } Because the child is a copy of the parent, any changes the child makes will occur in its copy of the data and won't be reflected in the parent. Including the initial parent process, how many processes are created by the program shown in Figure 3.32? Periodically, the init process calls wait() which ultimately releases the pid and entry in the process table of the zombie process. Once the parent process terminates, the init process becomes the new parent of the However, if a parent does not invoke wait(), the child process remains a zombie as long as the parent remains alive. When this occurs, the process id as well as entry in the process table are both released. When a process is terminated, it briefly moves to the zombie state and remains in that state until the parent invokes a call to wait(). It is important to note that the server must send a second ACK back to the client to inform the client the RPC has been performed.Įxplain the role of the init process on UNIX and Linux systems in regard to process termination. In situation (2), the server will receive a duplicate RPC and it will use the timestamp to identify it as a duplicate so as not to perform the RPC a second time. In situation (1), the use of ACKs allows the server ultimately to receive and perform the RPC. The client may not receive the ACK for one of two reasons: (1) the original RPC was never received by the server, or (2) the RPC was correctly received-and performed-by the server but the ACK was lost. If the client times out, it assumes the server was unable to perform the remote procedure so the client invokes the RPC a second time, sending a later timestamp. The client will then wait for one of two occurrences: (1) it will receive an ACK from the server indicating that the remote procedure was performed, or (2) it will time out. The client will also start a timeout clock. The general strategy is for the client to send the RPC to the server along with a timestamp. ![]() The general algorithm for ensuring this combines an acknowledgment (ACK) scheme combined with timestamps (or some other incremental counter that allows the server to distinguish between duplicate messages). The best way to become familiar with Process Monitor’s features is to read through the help file and then visit each of its menu items and options on a live system.The "exactly once" semantics ensure that a remote procedure will be executed exactly once and only once.
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