semaphore communication

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interprocess communication Quad (semaphore)

system releases the semaphore};3.3 Semctl function This function is used to directly control the semaphore information, its prototype is:int semctl (int sem_id, int sem_num, int command, ...); If there is a fourth argument, it is usually a union semum structure, defined as follows:Union semun{int Val;        struct Semid_ds *buf;unsigned short *arry; };The first two arguments are the same as in the previou

Linux interprocess communication-semaphore semget (), Semop (), Semctl ()

This article will describe the mechanism of a communication between processes-the semaphore. Note: Please do not confuse it with the previously mentioned signal, the signal and the semaphore are different two kinds of things. For more information about the signal, you can read my other article: Linux interprocess Communicatio

Linux-interprocess communication-semaphore

First, the conceptIn simple terms, the semaphore is a counter that describes the number of resources for a critical resource.The essence of Semaphore is a data operation lock, which does not have the function of data exchange, but realizes interprocess communication by controlling other communication resources (file, e

Examples of POSIX semaphore usage details for Linux interprocess communication

Use_posix_sem Sem_close (Semid); Sem_unlink (Mysem); #endif return 0; } Copy CodeOperation Result:$./a.outSem_val init=0Sem_val after Post=1Parent running!Parent running!Parent running!Parent running!Parent running!Parent EndChild running!Child running!Child running!Child running!Child running!Child EndProgam finishedAs you can see, the parent process executes before the child process executes 5 times after the post semaphore has been p

Linux Process Communication-semaphore usage

Linux Process Communication-semaphore usage-Linux general technology-Linux programming and kernel information. The following is a detailed description. I. Related Knowledge Semaphores: an integer; The number of resource entities that tables can be used by concurrent processes when the value is greater than or equal to 0; Number of processes waiting for using the critical section in the age of less than 0; T

Linux interprocess communication-semaphore

SetAll command struct seminfo *__buf; for Ipc_info commands};The return value of Sem_ctl success depends on the command parameter, which returns 1 on failure and sets the errnoSpecial Key Values ipc_private ( key parameter of the Semget function )Semget callers can give them Key the parameters pass a special key value ipc_pricate ( Its value is 0) . This allowsthesemget to create a new semaphore regardless of whether the

Linux interprocess communication-semaphore

; For GetAll and SetAll command struct seminfo *__buf; for Ipc_info commands};The return value of Sem_ctl success is determined by the command parameter, which returns 1 on failure and sets the errnoSpecial Key Values ipc_private ( key parameter of the Semget function )Semget callers can give them Key parameter to pass a special key value ipc_pricate ( Its value is 0) , so whether or not the semaphore already exists, Semget wi

Linux inter-process communication (System V) --- semaphore

Linux inter-process communication (System V) --- semaphoreSemaphore IPC Principle Semaphore communication mechanism is mainly used to synchronize processes to avoid concurrent access to shared resources. Semaphores can identify the number of available system resources. The simplest semaphores are binary semaphores. This is a conceptual diagram of the Linux

Ucos Real-time Operating system learning notes-inter-mission communication (semaphore)

Ucos Real-time operating system of inter-mission communication there are many kinds, I mainly study the SEM, mutex, queue, messagebox these four kinds. System kernel code, these kinds of tasks between the implementation mechanism of the communication mechanism is similar, next record my knowledge of the core code, for later back to see, but it is regrettable that did not carefully learn the extension code o

Linux Process Communication-semaphore usage

Title: Linux Process Communication-use semaphores I. Related KnowledgeSemaphores: an integer;The number of resource entities that tables can be used by concurrent processes when the value is greater than or equal to 0;Number of processes waiting for using the critical section in the age of less than 0;The initial semaphore value used for mutex must be greater than 0;It can only be changed through P and V pr

The way of process communication (IPC) under Linux-the semaphore

1. Related ConceptsSemaphore: The essence is a kind of data operation Lock, it does not have the function of data exchanging, but realizes inter-process communication through other communication resources (file, external device), which is an external resource identifier itself. Equivalent to a counter, record the number of resources available within the critical resource, and ensure that resources are avail

Signal, semaphore, lock, condition variable, message communication, shared memory, RPC (ii)

Well-known semaphore SemphoreIf the signal is a mechanism for the association of external events and processes, then semaphores are the mechanism of communication between processes and threads. Depending on whether the communication between different processes is supported or a different thread within the same process, the se

Linux interprocess communication (Message Queue/semaphore + shared memory)

used to control shared memory, which is prototyped as follows:int shmctl(int shm_id, int command, struct shmid_ds *buf); ResourcesAll of the above information is from the following websites: Linux interprocess communication (v): Semaphore Semget (), Semop (), Semctl () Linux interprocess communication (vi): Shared memory Shmget (), Shmat (),

Operation of semaphore for process communication

Overview of semaphores: Semaphores are a process communication mechanism used to resolve synchronization and mutex issues between processes, including a variable called semaphore and a process waiting queue that waits for resources under that semaphore, as well as two atomic operations on the semaphore process (PV oper

Unknown semaphore of process communication

Unknown semaphore of process communicationLike a well-known semaphore, a nameless signal is also the primary means of communication between processes/threads, except that he cannot be used between different processes. Of course, if you put the nameless semaphore in shared memory that can be accessed by multiple process

interprocess Communication-Semaphore

Semaphore: It describes the current quantity of a resource. It is intended for inter-process synchronization, which is equivalent to a counter, which itself does not have the function of data exchange, but rather by controlling other communication resources to achieve interprocess communication.When a process to access critical resources, the first to carry out the P operation request resources, when greate

Operating system-process/thread internal communication-semaphore, PV operation implementation and application (to solve the problem of philosophers eating and producer consumers)

The main content of this article: The realization of signal volume Using semaphores to solve the problem of philosophers ' dining Using semaphores to solve producer consumer problems first, the realization of the signal volume1.1 semaphore Structurestruct { int value; struct process * list} semaphore;Value represents the number of current semaphores that can be used, and the li

Process Communication (semaphore)

The essence of the semaphore is a data manipulation lock, which itself does not have the function of data exchange, but by controlling otherCommunication resources (files, external devices) to enable interprocess communication, which is itself an identification of an external resource. SignalIn this process is responsible for the data operation of mutual exclusion, synchronization and other functions.When a

Linux_c Development (5-6) interprocess communication _ Semaphore

Inter-process Communication _ semaphore Signal volume (known: semaphore) and other processes of communication between the same way, the main purpose is ** protect critical resources ** . The process can determine, based on it, whether certain shared resources can be accessed. In addition to access control, it can

Process Communication (ii)--Semaphore & memory Sharing

Memory sharing is a common way of communication between processes, enabling two completely independent process communication. When accessing shared memory, there is also a need for the semaphore for access control. Use the IPCS-M command to view system shared memory and IPCE-M + key to delete the specified shared memory. For

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