livelock


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livelock

(parallel)
/li:v'lok/ When two or more processes continuously change their state in response to changes in the other process(es) without doing any useful work.

This is similar to deadlock in that no progress is made but differs in that neither process is blocked or waiting for anything.

A human example of livelock would be two people who meet face-to-face in a corridor and each moves aside to let the other pass, but they end up swaying from side to side without making any progress because they always move the same way at the same time.

livelock

An endless loop in program execution. It occurs when a process repeats itself, because it continues to receive erroneous information. It can also occur when a process that calls another process is itself called by that process, and there is no logic to detect this situation and stop the operation. A livelock differs from a "deadlock," in that processing continues to take place, rather than just waiting in an idle loop. See deadly embrace.
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Livelock puts you in control of a huge mechanical monster that has a human consciousness.
Note that the net may be unsound if it contains a deadlock (a nonterminal marking where there are not enough resources to proceed any further even with one single step) or a livelock (there are always enough resources to make a following step, but all possible steps are not "progress"-steps, i.
Mogul and Ramakrishan [1997] describe a system that uses interrupts under normal network load and polling under overload, in order to avoid receiver livelock.
Routing algorithms that route packets along the set of channels identified in Step 1 and use only the turns from one set to another allowed by Steps 4 through 6 are deadlock free, livelock free, and highly adaptive.
SolidAC is a subset of Solidify, containing a module browser, RTL compilers, source code debugger and waveform display, and a set of automatic checks such as dead code, deadlock, livelock, clock crossing, constant signals, FSM checks, X propagation issues, array over-bound, reset, tri-state buses, and pragma.
In addition, Click processed packets at a lower priority than interrupts, leading to receive livelock [Mogul and Ramakrishnan 1997]: with increasing numbers of input packets, interrupt processing eventually starved all other system tasks, leading to reduced throughput.
Jade programmers need not deal with the complex phenomena such as deadlock, livelock, and starvation that characterize explicitly parallel programming.
Problems such as deadlock and livelock among processes are completely hardware independent.
Both Saphirus and CMR Design Automation will sell the complete Solidify line, which includes the Solidify property checking engine, SolidAC[TM] for automated checking of common design issues such as clock domain crossing, dead code, finite state machine (FSM) deadlock and livelock, case statement pragmas, reset propagation, bus contention, X assignment propagation, and array out-of-bounds, and SolidPC[TM] for AMBA protocol verification.
Any purely interrupt-driven system using fixed interrupt priorities will suffer from receive livelock under input overload conditions.