27Interprocess Communication (IPC) Mechanism for processes to communicate and to synchronize their actions.Message system – processes communicate with each other without resorting to shared variables.IPC facility provides two operations:send(message) – message size fixed or variablereceive(message)If P and Q wish to communicate, they need to:establish a communication link between themexchange messages via send/receiveImplementation of communication linkphysical (e.g., shared memory, hardware bus)logical (e.g., logical properties)
44Many-to-Many ModelAllows many user level threads to be mapped to many kernel threads.Allows the operating system to create a sufficient number of kernel threads.Solaris 2Windows NT/2000 with the ThreadFiber package
46Threading Issues Semantics of fork() and exec() system calls. Thread cancellation.Signal handlingThread poolsThread specific data
47Pthreadsa POSIX standard (IEEE c) API for thread creation and synchronization.API specifies behavior of the thread library, implementation is up to development of the library.Common in UNIX operating systems.
50Windows 2000 Threads Implements the one-to-one mapping. Each thread contains- a thread id- register set- separate user and kernel stacks- private data storage area
51Linux Threads Linux refers to them as tasks rather than threads. Thread creation is done through clone() system call.Clone() allows a child task to share the address space of the parent task (process)
52Java Threads Java threads may be created by: Extending Thread classImplementing the Runnable interfaceJava threads are managed by the JVM.