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deadlock

[′ded‚läk]
(computer science)
A situation in which a task in a multiprogramming system cannot proceed because it is waiting for an event that will never occur. Also known as deadly embrace; interlock; knot.

deadlock

1. A lock equipped with a dead bolt only.
2. A lock in which a bolt is moved by means of a key or thumb turn, and is positively stopped in its projected position.

deadlock

(parallel, programming)
A situation where two or more processes are unable to proceed because each is waiting for one of the others to do something.

A common example is a program waiting for output from a server while the server is waiting for more input from the controlling program before outputting anything. It is reported that this particular flavour of deadlock is sometimes called a "starvation deadlock", though the term "starvation" is more properly used for situations where a program can never run simply because it never gets high enough priority.

Another common flavour is "constipation", in which each process is trying to send stuff to the other but all buffers are full because nobody is reading anything). See deadly embrace.

Another example, common in database programming, is two processes that are sharing some resource (e.g. read access to a table) but then both decide to wait for exclusive (e.g. write) access.

The term "deadly embrace" is mostly synonymous, though usually used only when exactly two processes are involved. This is the more popular term in Europe, while deadlock predominates in the United States.

Compare: livelock. See also safety property, liveness property.
References in periodicals archive ?
Wednesday, jurors indicated they still were deadlocked.
The jury hearing Raymundo's case found the defendant not guilty of four counts of attempted murder but deadlocked 11-1 in favor of guilty on the remaining charges of assault and shooting at an inhabited vehicle, Deputy District Attorney Carlos Chung said.
2), a node such that every one of its neighbors knows that is deadlocked, also updates its variable deadlock to true.
Counsel should make timely objection when the specter of coercion enshrouds a deadlocked jury if the error is to be exorcised on appeal.
However, Mr Prescott's legal moves to break the deadlocked dispute were backed in the Commons by 284 votes to 59.
Jurors in the case of retired Catholic priest Michael Wempe reached a verdict Friday on one count of child molestation but remained deadlocked on four others.
They were still deadlocked at 3-3 after the penalty shoot out and McDonald's winner in sudden death was greeted with shock by gallant UUJ who lost goalkeeper Shane Wilson with a broken finger in 85 minutes.
March 8 /PRNewswire/ -- Last night, in a 4-4 vote, the Albuquerque City Council deadlocked on the city administration's request for support of a stipulation filed to reduce Public Service Co.
Signaling potential divisions in the county's biggest labor union just two days after its top leader resigned, officials emerged from a more than two-hour, closed-door session Thursday saying they had deadlocked over naming a successor.
Negotiations in South Africa aimed at ending the political crisis in neighbouring Zimbabwe are deadlocked, opposition leader Morgan Tsvangirai's spokes-man said yesterday.
Regarding the other patent, the jury found noninfringement on one of the two claims and the judge declared the jury deadlocked on the remaining claim.
Right now talks are deadlocked," a 3i spokesman said.