ipc 4300

of the pipeline, and the read process reads data in the header of the pipeline. 【Note:After the data is read by a process, it will be deleted from the pipeline, and other read processes will no longer be able to read the data. Pipeline providesSimple Flow Control MechanismWhen a process tries to read an empty MPs queue, the process will be blocked. Similarly, when the pipeline is full, the process attempts to write data to the pipeline, and the process will be blocked .] Category: Unknown pipel

1 pipe (PIPE) Pipelines are the oldest form of IPC in Unix systems, and all UNIX systems provide such communication mechanisms, including Linux. The following restrictions apply to using MPs pipelines: 1. due to historical reasons, the pipeline is half-duplex and data can only flow in one direction. To achieve bidirectional communication, you must create two pipelines. 2. Both parties of the pipeline communication must be kinship-related processes

client thread Public Synchronized Void Setvalue (writable value ){ This . Value = Value; callcomplete ();} Protected Synchronized Void Callcomplete (){ This . Done = True ; Notify (); // Notify caller } 4.Asynchronous/Synchronization Model The external interfaces of hadoop RPC are actually synchronous, but the internal implementation of RPC is actually an asynchronous message mechanism. Hadoop uses the thread wait/notify mechanism to Implement

1. concept:A socket is a network IPC interface that allows a process to communicate with other processes. through this interface, other processes run transparently on the same computer or on different computers. that is to say, it supports inter-process communication within the computer and inter-process communication between the computer. The socket interface can adopt many different network protocols, but we mainly discuss the network communication

Linux inter-process communication (IPC) programming practices (10) System V semaphores --- typical PV operations// P primitive // P (semaphore * S)Wait (semaphore * S ){-- S-> value; if (S-> value {// Set the current process to blocking// Insert the PCB of the current process into the block queue S-> block (S-> list) at the end of the list );}}[// V primitive // V (semaphore * S)Signal (semaphore * S ){+ + S-> value; if (S-> value {// Wake up a proces

; Char**s_aliases; intS_port; Char*S_proto;}; #includestructServent *getservbyname (Const Char*name,Const Char*Proto)structServent *getservbyprot (intPortConst Char*Proto)structServent *getservent ()voidSetservent (intStayopen)voidEndservent ()Sockets and Address bindings:#include bindings:int bind (int sockfd,conststruct SOCKADDR *addr,socklen_t len) View socket binding address:int getsockname (int sockfd,struct SOCKADDR *addr,socklen_t len) View the address of the socket connection:int getpeer

Linux IPC parameter settings-command method: Echo 80>/proc/sys/Vm/overcommit_ratio, etc Msgmnb Maximum byte limit for each message queue. Msgmni The maximum number of message queues of the entire system. Msggsz The size (in bytes) of the message segment ). Messages greater than this value are divided into multiple segments. Msgseg The maximum number of message segments that can exist in a single queue. Msgtql The maximum number of messages in the

right knife and fork if (Semop (Semid, sops, 1) = =-1) err_exit ("Wait_2fork error");} *///release two cutlery void signal_2fork (unsigned short) {unsigned short left = no; unsigned short right = (no+1)%5; struct SEMBUF sops[2] = {{left, 1, 0}, {right, 1, 0}}; if (Semop (Semid, SOPs, 2) = =-1) err_exit ("Signal_2fork error");} philosopher void philosopher (Unsigned Short No) {Srand (Time (NULL)); while (true) {cout int main () { //Creates a semaphore set: Contains 5 semaphore

the same semantics. ).Open rules for Named pipes1) Read Open FIFOO_nonblock Disable (blocked): block until a corresponding process has opened the FIFO for writeO_nonblock Enable(non-blocking): Return to success immediatelyExample 1: Blocking, read-only open int main () { int fd = open ("FIFO", o_rdonly); if (fd = =-1) err_exit ("FIFO open Error"); cout Example 2: Read-only, non-blocking open int main () { int fd = open ("FIFO", o_rdonly| O_nonblock); if (fd = =-1) e

Sem_undo data structure adjustment queue for this process (on the entry for this semaphore). For example, if the action value is 2, then this adds 2 to the adjustment entry for the semaphore. when a process is deleted, such as when it exits, Linux traverses its Sem_undo data structure group and implements adjustments to the semaphore array. If the semaphore is removed, its sem_undo data structure remains in the task_struct queue of the incoming signal, but the corresponding semaphore array iden

Message Queuing in the system:# IPCS------Message Queues--------Key msqid owner perms used-bytes messages 0x001fffde 229376 root 0 0 0 When the user presses CTRL + C, the program deletes the message queue, presses CTRL + C, and then views:# IPCS------Message Queues--------Key msqid owner perms used-bytes messages You can see that the deletion in the program is successful.POSIX Message Queuing is roughly

How to communicate between processes:1) There are also named pipes and non-named pipes in the pipeline, non-named pipes can only be used for parent-child process communication, named pipes can be used for non-parent-child processes, named Pipes are FIFO, pipeline is a first-out communication mode. FIFO is a first-in-one-out queue. It is similar to a pipeline that allows only one-way flow of data. Each FIFO has a name that allows unrelated processes to access the same FIFO and therefore also beco

for deleting the FIFO file isint unlink (const char *pathname);Example:#include 3.2 Open, close FIFO fileThe open and close functions are the same as opening/closing more common files for FIFO types of files. Using O_wronly to open the write end of the FIFO, with the o_rdonly option, the read-in end of the FIFO is opened, and the write read-in can be opened simultaneously by several processes. Fd_recv=open (argv[1],o_rdonly);Fd_send=open (argv[2],o_wronly);if (fd_send==-1) {Perror ("Fd_send");E

As the oldest interprocess communication method, the pipeline has the following features:1. Exist in all UNIX implementations.2. No name, so it can only be used by a related process.3. It is created by the function pipe, accessed by the read and write functions, but only provides one-way (one-way) traffic.Return two file descriptor via parameter FD: fd[0] Open for Read, fd[1] for write. The output of fd[1] is the input of fd[0].Macro S_isfifo can be used to determine whether a descriptor or file

the atomicity of writes, and the pipeline buffer has an idle area, and the write process attempts to write data to the pipeline. If the read process does not read the data in the pipeline buffer, the write operation will be blocked.Note: Writing data to a pipeline is meaningful only if the read side of the pipeline exists. Otherwise, the process that writes data to the pipeline receives the sifpipe signal from the kernel, which the application can process or ignore (the default action is the ap

character to the first character passed to the program's parameters. The first process initiated at the same time is also responsible for the deletion of semaphores.Assuming the semaphore is not removed, it will continue to exist in the system. Even if the program has exited, it may cause problems the next time you execute the program, and the semaphore is a limited resource.Call Semget in the main function to create a semaphore that returns a semaphore identifier that is stored in the global v

, which means there are currently no resources available. P Operation: If there are available resources (semaphore value >0), then occupy a resource (give the semaphore value minus one, enter the critical section code). If no resources are available (the semaphore value equals 0), it is blocked until the system assigns the resource to the process (into the wait queue until the resource turns to the process).V Operation: If there is a process waiting for a resource in the waiting queue for the s

In Android, each application is made up of activity and service that are likely to run in the same process or run in different processes. So, how does the activity or service in the same process communicate? This is the binder interprocess communication mechanism to be described in this article.We know that the Android system is based on the Linux kernel, while the Linux kernel inherits and is compatible with the rich Unix system interprocess communication (