Concurrency control

variable that is changed (e.g., incremented, decremented, toggled) depending on programmer-defined conditions, used to control access to a common resource by multiple processes in a concurrent system

In computer science, ACID (atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. For example, a transfer of funds from one bank account to another, involving multiple changes such as debiting one account and crediting another, is a single transaction.

protected section of code that cannot be executed by more than one process at a time

computer programming technique in which a process repeatedly checks to see if a condition is true

property of concurrency control, which is instituted for the purpose of preventing race conditions

in concurrent programming, an object or module intended to be used safely by more than one thread

synchronization mechanism for enforcing limits on concurrent access to a resource

concurrency control method commonly used by database management systems

undesirable computing scheduling scenario

form of input/output processing

coarse-grained mutex used in some process virtual machines

measures to ensure concurrent computing operations generate correct results

In computer science, the test-and-set instruction is an instruction used to write (set) a flag value to a memory location and return its old value as a single atomic (i.e., non-interruptible) operation. The caller can then "test" the result to see if the state was changed by the call. If multiple processes may access the same memory location, and if a process is currently performing a test-and-set, no other process may begin another test-and-set until the first process's test-and-set is finished. A central processing unit (CPU) may use a test-and-set instruction offered by another electronic c

computer synchronization mechanism that enforces an ordering on operations before and after the barrier

in some programming languages (C, C++, C#, Java), a variable specially marked to disable optimizations because its value may change between accesses even if it does not appear to be modified; primarily used in hardware access and in threading

In computer science, compare-and-swap (CAS) is an atomic instruction used in multithreading to achieve synchronization. It compares the contents of a memory location with a given (the previous) value and, only if they are the same, modifies the contents of that memory location to a new given value. This is done as a single atomic operation. The atomicity guarantees that the new value is calculated based on up-to-date information; if the value had been updated by another thread in the meantime, the write would fail. The result of the operation must indicate whether it performed the substitution

abstract model to describe execution of transactions running in the system

class of algorithms

design pattern only locking if the locking criterion check indicates that locking is required

aspect of an operating system

concurrency control locking protocol in databases and transaction processing

Concurrency control method

concurrency control mechanism, analogous to database transactions for controlling access to shared memory in concurrent computing, that simplifies concurrent programming by allowing a group of load and store instructions to execute in an atomic way

In computer science, the fetch-and-add (FAA) CPU instruction atomically increments the contents of a memory location by a specified value.

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In computing, a futex (short for "fast userspace mutex") is a kernel system call that programmers can use to implement basic locking, or as a building block for higher-level locking abstractions such as semaphores and POSIX mutexes or condition variables.

In computer science, load-linked/store-conditional (LL/SC), sometimes known as load-reserved/store-conditional (LR/SC), are a pair of instructions used in multithreading to achieve synchronization. Load-link returns the current value of a memory location, while a subsequent store-conditional to the same memory location will store a new value only if no updates have occurred to that location since the load-link. Together, this implements a lock-free, atomic, read-modify-write operation.

concurrency control mechanism for controlling access to shared memory in concurrent computing

lock used in the kernel to provide concurrency control required by symmetric multiprocessing systems

In computer science, read-copy-update (RCU) is a synchronization mechanism that avoids the use of lock primitives while multiple threads concurrently read and update elements that are linked through pointers and that belong to shared data structures (e.g., linked lists, trees, hash tables).

optimistic concurrency control method for group editing

Formal specification language in computer science

In computer science, read–modify–write is a class of atomic operations (such as test-and-set, fetch-and-add, and compare-and-swap) that both read a memory location and write a new value into it simultaneously, either with a completely new value or some function of the previous value. These operations prevent race conditions in multi-threaded applications. Typically they are used to implement mutexes or semaphores. These atomic operations are also heavily used in non-blocking synchronization.