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Thread Control Block (TCB) is a data structure in an operating system kernel that contains thread-specific information needed to manage the thread. [1] The TCB is "the manifestation of a thread in an operating system." Each thread has a thread control block. An operating system keeps track of the thread control blocks in kernel memory. [2]
The startup function startup_32() for the kernel (also called the swapper or process 0) establishes memory management (paging tables and memory paging), detects the type of CPU and any additional functionality such as floating point capabilities, and then switches to non-architecture specific Linux kernel functionality via a call to start ...
A task (i.e., a synonym for thread) is the minimal entity that Linux can schedule. However, it can also manage groups of threads, whole multi-threaded processes, and even all the processes of a given user. This design leads to the concept of schedulable entities, where tasks are grouped and managed by the scheduler as a whole.
Diagram of a monolithic kernel. In a monolithic kernel, all OS services run along with the main kernel thread, thus also residing in the same memory area. This approach provides rich and powerful hardware access. UNIX developer Ken Thompson stated that "it is in [his] opinion easier to implement a monolithic kernel". [34]
Multiple threads can interfere with each other when sharing hardware resources such as caches or translation lookaside buffers (TLBs). As a result, execution times of a single thread are not improved and can be degraded, even when only one thread is executing, due to lower frequencies or additional pipeline stages that are necessary to accommodate thread-switching hardware.
Unix systems use a centralized operating system kernel which manages system and process activities. All non-kernel software is organized into separate, kernel-managed processes. Unix systems are preemptively multitasking : multiple processes can run at the same time, or within small time slices and nearly at the same time, and any process can ...
In computer operating systems, a light-weight process (LWP) is a means of achieving multitasking.In the traditional meaning of the term, as used in Unix System V and Solaris, a LWP runs in user space on top of a single kernel thread and shares its address space and system resources with other LWPs within the same process.
Threads have their own thread ID, program counter (PC), a register set, and a stack, but share code, heap data, and other resources with other threads of the same process. [87] [88] Thus, there is less overhead to create a thread than a new process. [89] On single-CPU systems, concurrency is switching between processes.