deadlock


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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.

deadly embrace

A stalemate that occurs when two elements in a process are each waiting for the other to respond. For example, in a network, if one user is working on file A and needs file B to continue, but another user is working on file B and needs file A to continue, each one waits for the other. Both are temporarily locked out. The software must be able to deal with this. Contrast with livelock.
References in periodicals archive ?
Key Control Deadlock Test: Mike Garza, Masten Group
But you still have time to make sure that your operating agreement identifies the issues that arise between you, resolves them in a way that makes sense to both of you, and contains appropriate deadlock provisions.
In this section, we overview the step look-ahead method that can help us to find out the deadlock markings.
The vote has gone to deadlock four times this series with judges Louis Walsh, Mel B, Cheryl Fernandez-Versini and Simon Cowell.
The Doha trade talks have been deadlocked since 2008 over differences on major issues between members including agriculture, industrial tariffs and non-tariff barriers, services and trade remedies.
The presidential election was once again taken towards a deadlock after Abdullah Abdullah announced his team's stance regarding the electoral process and said his team will not accept the outcome of election.
Cowell is still looking for a solution to deadlock and is thought to be considering extra-time and penalties.
Complaining about the lack of a culture of compromise in Turkey, CHP deputy TE-rmen said the deadlock was due to the inflexible red lines of the various parties.
It goes on to say that the UN chief expressed the hope that the two leaders would overcome this deadlock during the upcoming visit of his Special Adviser, from4 to 8 November, and resolve any other outstanding issues so that the date for the first leaders` meeting can be set and full-fledged negotiations can resume without further delay.
Dannii voted for the female soloist to be sent home, while Ronan passed the task to the Australian public and voted for the trio to be eliminated for the decision to come to a deadlock.
We hope that overcoming the deadlock in the Conference, will accelerate the ongoing work in the fields of disarmament, arms control and non-proliferation," the MFA said.