msgque(国外英语资料).docVIP

msgque(国外英语资料) In UNIX, a process makes another entity perform a transaction, and the action taken is a sub process of fork. The child process copies only the data area of the parent process to its own data area. In accordance with the POSIX standard UNIX operating system, the same process threads to share process instructions, most of the data (except for thread private data), signal processing methods, processes, operating environment. Because the thread shares the global variables of the process, it can share the data with the message queue written by the user himself. Build a multitasking model and implement it with threads The UNIX operating system that meets the POSIX standard provides control functions for threads, such as creation and termination of threads, mutex between threads, synchronization among threads, and so on. Using these system functions, the message queue can be successfully simulated to realize data sharing and synchronization among threads, so as to accomplish the real-time performance of multi tasks. To successfully describe data sharing and synchronization between threads, take the following task model as an example. First, the message queue property data structure is established #define MAXQUEUE 30 Typedef, struct, mq_attrib { Char name[20]; Pthread_mutex_t mutex_buff; Pthread_mutex_t mutex_cond; Pthread cond_t cond; Int maxElements; Int elementLength; Int curElementNum; Caddr_t buff; }mq_attrib, mq_attribstruct, mq_attrib_t apparatus; Mq_attrib_t msqueue[MAXQUEUE]; The data structure defines the message queue name name, maximum message number maxElements, a single message length is elementLength, the current message number curElementNum, stored message buffer buff, buffer protection lock mutex_buff, thread synchronization variables cond, mutex_cond variable thread synchronization lock protection. Creation of a message queue Create a message queue based on this data structure. The function is msqueue_create (parameter interpretation: name,