Search results
Results from the WOW.Com Content Network
lock contention: this occurs whenever one process or thread attempts to acquire a lock held by another process or thread. The more fine-grained the available locks, the less likely one process/thread will request a lock held by the other. (For example, locking a row rather than the entire table, or locking a cell rather than the entire row);
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:
The original semaphore bounded buffer solution was written in ALGOL style. The buffer can store N portions or elements. The "number of queueing portions" semaphore counts the filled locations in the buffer, the "number of empty positions" semaphore counts the empty locations in the buffer and the semaphore "buffer manipulation" works as mutex for the buffer put and get operations.
(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?"
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 ...
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 ...
Java synchronized blocks, in addition to enabling mutual exclusion and memory consistency, enable signaling—i.e. sending events from threads which have acquired the lock and are executing the code block to those which are waiting for the lock within the block. Java synchronized sections, therefore, combine the functionality of both mutexes ...
With priority ceiling protocol, the shared mutex process (that runs the operating system code) has a characteristic (high) priority of its own, which is assigned to the task of locking the mutex. This works well, provided the other high-priority task(s) that tries to access the mutex does not have a priority higher than the ceiling priority.