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The introduction of granular (subset) locks creates the possibility for a situation called deadlock. Deadlock is possible when incremental locking (locking one entity, then locking one or more additional entities) is used. To illustrate, if two bank customers asked two clerks to obtain their account information so they could transfer some money ...
The term "deadlock avoidance" appears to be very close to "deadlock prevention" in a linguistic context, but they are very much different in the context of deadlock handling. Deadlock avoidance does not impose any conditions as seen in prevention but, here each resource request is carefully analyzed to see whether it could be safely fulfilled ...
Distributed deadlocks can be detected either by constructing a global wait-for graph, from local wait-for graphs at a deadlock detector or by a distributed algorithm like edge chasing. Phantom deadlocks are deadlocks that are detected in a distributed system due to system internal delays but no longer actually exist at the time of detection.
This subtlety can increase the chance that a programmer will unknowingly introduce a deadlock. [citation needed] In a database management system, for example, a lock could protect, in order of decreasing granularity, part of a field, a field, a record, a data page, or an entire table. Coarse granularity, such as using table locks, tends to give ...
Mimer SQL is a DBMS that only implements optimistic concurrency control. [10] Google App Engine data store uses OCC. [11] The Apache Solr search engine supports OCC via the _version_ field. [12] The Elasticsearch search engine updates its documents via OCC. Each version of a document is assigned a sequence number, and newer versions receive ...
Deadlock freedom can be expanded to implement one or both of these properties: Lockout-freedom guarantees that any process wishing to enter the critical section will be able to do so eventually. This is distinct from deadlock avoidance , which requires that some waiting process be able to get access to the critical section, but does not require ...
Semaphore locking also has a time limit to prevent a deadlock condition in which a lock is acquired by a single process for an infinite time, stalling the other processes that need to use the shared resource protected by the critical section.
Deadlock commonly refers to: Deadlock (locksmithing) or deadbolt, a physical door locking mechanism; Deadlock (computer science), a situation where two processes are each waiting for the other to finish; Political deadlock or gridlock, a situation of difficulty passing laws that satisfy the needs of the people