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While a binary semaphore may be colloquially referred to as a mutex, a true mutex has a more specific use-case and definition, in that only the task that locked the mutex is supposed to unlock it. This constraint aims to handle some potential problems of using semaphores:
Two nodes, i and i + 1, being removed simultaneously results in node i + 1 not being removed. In computer science, mutual exclusion is a property of concurrency control, which is instituted for the purpose of preventing race conditions.
In computer science, a semaphore is a variable or abstract data type used to control access to a common resource by multiple threads and avoid critical section problems in a concurrent system such as a multitasking operating system. Semaphores are a type of synchronization primitive. A trivial semaphore is a plain variable that is changed (for ...
(Mutex "m" shall not be // a spin-lock.) acquire (m); // Now, we are holding the lock and can check the condition for the // first time. // The first time we execute the while loop condition after the above // "acquire", we are asking, "Does the condition/predicate/assertion // we are waiting for happen to already be true?"
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. A futex consists of a kernel-space wait queue that is attached to an atomic integer in ...
There are several possible solutions, but all solutions require a mutex, which ensures that only one of the participants can change state at once.The barber must acquire the room status mutex before checking for customers and release it when they begin either to sleep or cut hair; a customer must acquire it before entering the shop and release it once they are sitting in a waiting room or ...
Alternatively an RW lock can be implemented in terms of a condition variable, cond, an ordinary (mutex) lock, g, and various counters and flags describing the threads that are currently active or waiting. [7] [8] [9] For a write-preferring RW lock one can use two integer counters and one Boolean flag:
But if the function is used in a reentrant interrupt handler and a second interrupt arises while the mutex is locked, the second routine will hang forever. As interrupt servicing can disable other interrupts, the whole system could suffer. The same function can be implemented to be both thread-safe and reentrant using the lock-free atomics in ...