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 deadlyembrace.

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, livenessproperty.

[Jargon File]

(2000-07-26)