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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 ?
Finally, it declares the nodes 1,3,4,5,7,8 and 9 as deadlocked nodes.
In Figure 1, processes 1, 2, and 3 form a cycle, and are deadlocked.
4) However, trial judges may not stray far from a predetermined path when a deadlocked jury erects a barrier to case resolution.
In Moore's first trial, the Los Angeles jury convicted him of being a felon with a firearm, acquitted him of attempted torture, and deadlocked 11-1 in favor of guilt on attempted murder and 8-4 in favor of guilt on kidnapping.
19 shooting, but jurors deadlocked on another count of attempted murder and assault with a firearm.
The two deadlocked charges are aggravated arson, which requires premeditation and an attempt to cause injury to persons or property, and arson of a structure or forest with a special allegation that property in excess of $1 million was destroyed or damaged, Baum said.
Jeremy Morse smiles a bit after talking to his attorney, John Barnett, after the jury deadlocked in Morse's second assault trial in Los Angeles.
The first jury to hear the case deadlocked 7-5 last July 29 in favor of convicting Morse.
Jurors in the trial of two men charged with murdering a 17-year-old Hoover High School student were ordered to resume deliberations Wednesday after announcing they were deadlocked on four of six charges.
With the election apparently deadlocked, the seat could be vacant indefinitely.
A Van Nuys Superior Court jury found Frank Boyd Cockrell, 55, guilty of two counts of solicitation of murder, not guilty of a third, and deadlocked on a fourth count.
Over the summer, there were seven Antelope Valley districts with deadlocked contract negotiations.