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The request was directed at a server that is not able to produce a response (for example because of connection reuse). 422 Unprocessable Content The request was well-formed (i.e., syntactically correct) but could not be processed. [1]: §15.5.21 423 Locked (WebDAV; RFC 4918) The resource that is being accessed is locked. [7]
If locking is used, other users who attempt to edit the same record must wait until the first user's lock times out. HTTP does provide a form of built-in OCC. The response to an initial GET request can include an ETag for subsequent PUT requests to use in the If-Match header. Any PUT requests with an out-of-date ETag in the If-Match header can ...
Written in C and Python, CPython is the default and most widely used implementation of the Python language. CPython can be defined as both an interpreter and a compiler as it compiles Python code into bytecode before interpreting it.
Before being introduced to lock granularity, one needs to understand three concepts about locks: lock overhead: the extra resources for using locks, like the memory space allocated for locks, the CPU time to initialize and destroy locks, and the time for acquiring or releasing locks. The more locks a program uses, the more overhead associated ...
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 progress. Hence, if two threads can contend for the same mutex lock or spinlock, then the algorithm is not lock-free. (If we suspend one thread that holds the lock, then the second ...
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:
File locking is a mechanism that restricts access to a computer file, or to a region of a file, by allowing only one user or process to modify or delete it at a specific time, and preventing reading of the file while it's being modified or deleted.
Some laptops and compact keyboards also have a Function Lock - FN Lock. On these devices, a Fn modifier key is used to combine keys to save room and add non-standard functionality; a common use is merging the row with keys F1- F12 with keys that adjust settings such as display brightness, media volume and playback, and keyboard illumination. Fn ...