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An algorithm is lock-free if, when the program threads are run for a sufficiently long time, at least one of the threads makes progress (for some sensible definition of progress). All wait-free algorithms are lock-free. In particular, if one thread is suspended, then a lock-free algorithm guarantees that the remaining threads can still make ...
In software engineering, double-checked locking (also known as "double-checked locking optimization" [1]) is a software design pattern used to reduce the overhead of acquiring a lock by testing the locking criterion (the "lock hint") before acquiring the lock. Locking occurs only if the locking criterion check indicates that locking is required.
Read-copy-update insertion procedure. A thread allocates a structure with three fields, then sets the global pointer gptr to point to this structure.. A key property of RCU is that readers can access a data structure even when it is in the process of being updated: RCU updaters cannot block readers or force them to retry their accesses.
It alerts the client to wait for a final response. The message consists only of the status line and optional header fields, and is terminated by an empty line. As the HTTP/1.0 standard did not define any 1xx status codes, servers must not [ note 1 ] send a 1xx response to an HTTP/1.0 compliant client except under experimental conditions.
In AmigaOS, a lock on a file (or directory) can be acquired using the Lock function (in the dos.library). A lock can be shared (other processes can read the file/directory, but can't modify or delete it), or exclusive so that only the process which successfully acquires the lock can access or modify the object.
In computer architecture, the test-and-set CPU instruction (or instruction sequence) is designed to implement mutual exclusion in multiprocessor environments. Although a correct lock can be implemented with test-and-set, the test and test-and-set optimization lowers resource contention caused by bus locking, especially cache coherency protocol overhead on contended locks.
Sending cache is changed in S and the requesting cache is set R/F (in read miss the "ownership" is always taken by the last requesting cache) – shared intervention. – In all the other cases the data is supplied by the memory and the requesting cache is set S (V). Data stored in MM and only in one cache in E (R) state.
This was a spurious wakeup, some other thread occurred // first and caused the condition to become false again, and we must // wait again. wait (m, cv); // Temporarily prevent any other thread on any core from doing // operations on m or cv. // release(m) // Atomically release lock "m" so other // // code using this concurrent data // // can ...