Unix™ Systems Programming [Electronic resources] : Communication, Concurrency, and Threads نسخه متنی

17.7 Concurrent Tasks

Modify the program to allow multiple computations and tasks. Use a MAX_TASKS value of 10 for this part. A new NEWTASK packet may come in before the data from previous tasks has been completely transmitted.

When a new NEWTASK packet comes in, find an available slot in the tasks object, create a new set of pipes, and fork a new child to execute the command. Don't enter any duplicates in the tasks array.

Figure 17.9 shows a schematic of a threaded NTPVM dispatcher that supports multiple simultaneous tasks. When another request comes in, the input thread creates a new output thread. Since multiple output threads write to standard output, define an additional mutex lock to synchronize output on the dispatcher's standard output.