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What 3 conditions must be present for deadlock to be possible?
In deadlock prevention, we constrain resource requests to prevent at least one of the four conditions of deadlock. This is either done Indirectly, by preventing one of the three necessary policy conditions (mutual exclusion, hold and wait, no preemption), or directly by preventing circular wait.
What are the deadlock conditions?
Four conditions that must hold for a deadlock to be possible: Mutual exclusion: processes require exclusive control of its resources (not sharing). Hold and wait: process may wait for a resource while holding others. irreversible: unable to reset to an earlier state where resources not held.
How can deadlock be resolved?
After a deadlock is detected, it can be corrected by using one of the following methods: Process termination: one or more processes involved in the deadlock may be aborted. One could choose to abort all competing processes involved in the deadlock. This ensures that deadlock is resolved with certainty and speed.
How can I avoid deadlocks?
The easiest way to avoid deadlocks is to be disciplined in your code. This can be achieved by ensuring that all the resources are accessed in the same order all the time. For example, if two concurrent transactions both started by requesting the lock for row 1 and later on requesting the lock for row 2.
How to avoid deadlock in MySQL?
To avoid deadlock, you must then make sure that concurrent transactions don’t update row in an order that could result in a deadlock. Generally speaking, try to acquire lock always in the same order even in different transaction (e.g. always table A first, then table B). Another reason for deadlock in database can be missing indexes.
Can deadlocks be prevented?
Deadlocks can be prevented by preventing at least one of the four required conditions: Shared resources such as read-only files do not lead to deadlocks. Unfortunately some resources, such as printers and tape drives, require exclusive access by a single process.