c - 同时运行两个共享内存的 C 程序，如何？

Question

我有两个 c 文件:producer.c 和 consumer.c。消费者在内存中创建一个共享缓冲区，等待生产者将项目放入缓冲区进行消费。生产者将共享内存附加到其内存映射，然后开始将项目放入缓冲区。

问题是如何将它们一起编译运行？

这是实际的任务。 (我知道我可以用一个使用线程的 c 文件来完成，但这不是我被要求做的。)

In this part you will develop a producer-consumer application that will use shared memory for process communication (POSIX shared memory, not System V shared memory). There will be N producers and N consumers. N can be 1, 2, or 3.

You will develop a producer program (producer.c) and a consumer program (consumer.c). When started, the producer program will create N child processes which will be acting as N producers (i.e. each child process will be a producer process).

Similarly, when started, the consumer program will create N child processes, where each child process will be acting as a consumer process. You will consider that consumers are identified as 0, 1, 2, depending on N. For example, if N is 2, then there will two consumers, 0 and 1.

The consumer program will be run first. When run, the consumer program will first create a shared memory of size 4 KB. This shared memory will be the place where you will have a shared single buffer sitting. The buffer can be accessed by producers and consumers. The buffer size is 100. It can hold at most 100 items (integers). In the shared memory you can have some other shared variables that you feel necessary. The consumer program will also create one or more semaphores (you decide how many).

Then it will create N child processes (N consumers) using the fork() system call (You will not need to use the exec() system call). The main process of the consumer program (parent), after creating the child processes, should not terminate. It should wait until all children (i.e. consumers) finish their tasks and terminate. When all children terminate, it will remove (delete) the shared memory from the system. It will also remove (delete) the semaphores. Then it can terminate as well.

Each producer will read an input file of positive integers (one integer per line) and will just pass the integers through a shared buffer sitting in a shared memory (created by the consumer program) between the producers and consumers.

Each consumer will read integers from the shared buffer and will write a received integer z to an output file associated with consumer if z mod N is equal to the ID of the consumer. For example, if N is 3 and if the ID of a consumer is 2 and the consumer has received an integer 7, it will do nothing with it (ignore), but if it receives 8, it will write the integer to its output file. An output file will contain one integer in a line. While producers and consumers are accessing the shared buffer, they should use semaphores so that access is synchronized. Additionally, if the buffer is full, producers should sleep, and if there is nothing to consume, consumers should sleep. We should not have busy waiting. You will use POSIX semaphores (named semaphores). The consumer program will be invoked as follows:
consumer N …

Here, N is the number of consumer processes to be created. The value of this parameter must be the same with the corresponding parameter of the producer program. Here, the is the name of the output file that will be used by the consumer with ID X. The number of output file names entered will be equal to N. is a name we can use to identify the shared memory. is a name we can use to identify the semaphores (it can be a prefix that can be used for names of many semaphores). These same names must be used when invoking the producer. The producer program will be named as producer and will be invoked with the following parameters:
producer N …

Here, N is the number of producers. The is the name of an input file for producer X. An input file is a text file storing integers. The number of input file names we enter will be equal to N. There can be one or more integers in a file. An input file can be quite huge (billions of integers). is a name we can use to identify the shared memory. is a name we can use to identify the semaphores.

An example invocation of the programs can be like the following.
consumer 3 out0.txt out1.txt out2.txt mysmem mysemaphores producer 3 in0.txt in1.txt in2.txt mysmem mysemaphore

Answer 1

问题是如何同步共享内存的两个进程。你可以使用 Posix semaphores ，但还有许多其他方法可以做到这一点。