Deadlock Prevention:
o Preventing deadlocks by constraining how
requests for resources can be made in the system and how
they are handled (system design).
o The goal is to ensure that at least one of the
necessary conditions for deadlock can never hold.
*
Deadlock Avoidance:
o The system dynamically considers every request
and decides whether it is safe to grant it at this point,
o The system requires additional apriori
information regarding the overall potential use of each
resource for each process.
o Allows more concurrency.
Similar to the difference between a traffic light
and a police officer directing traffic.
* Deadlock deduction:-
Often, neither avoidance nor deadlock
prevention may be used. Instead deadlock detection and
process restart are used by employing an algorithm that
tracks resource allocation and process states, and rolls
back and restarts one or more of the processes in order to
remove the deadlock. Detecting a deadlock that has already
occurred is easily possible since the resources that each
process has locked and/or currently requested are known to
the resource scheduler or OS.
Detecting the possibility of a deadlock before it occurs is
much more difficult and is, in fact, generally undecidable,
because the halting problem can be rephrased as a deadlock
scenario. However, in specific environments, using specific
means of locking resources, deadlock detection may be
decidable. In the general case, it is not possible to
distinguish between algorithms that are merely waiting for a
very unlikely set of circumstances to occur and algorithms
that will never finish because of deadlock.
Deadlock detection techniques include, but is not limited
to, Model checking. This approach constructs a Finite
State-model on which it performs a progress analysis and
finds all possible terminal sets in the model. These then
each represent a deadlock.
safety algorithm is algo which is used for deadlock avoidance.
A deadlock is a situation wherein two or more competing actions are waiting for the other to finish, and thus neither ever does. It is often seen in a paradox like 'the chicken or the egg'. " When two trains approach each other at a crossing, both shall come to a full stop and neither shall start up again until the other has gone.
a. The creation and deletion of both user and system processes b. The suspension and resumption of processes c. The provision of mechanisms for process synchronization d. The provision of mechanisms for process communication e. The provision of mechanisms for deadlock handling
In order for deadlock to occur, four conditions must be true.Mutual exclusion - Each resource is either currently allocated to exactly one process or it is available. (Two processes cannot simultaneously control the same resource or be in their critical section).Hold and Wait - processes currently holding resources can request new resourcesNo preemption - Once a process holds a resource, it cannot be taken away by another process or the kernel.Circular wait - Each process is waiting to obtain a resource which is held by another process.
a. The creation and deletion of both user and system processes b. The suspension and resumption of processes c. The provision of mechanisms for process synchronization d. The provision of mechanisms for process communication e. The provision of mechanisms for deadlock handling
safety algorithm is algo which is used for deadlock avoidance.
deadlock avoidance of windows 7
Deadlock avoidance involves ensuring that the system never enters a deadlock state by using techniques like resource allocation strategies (e.g., Banker's algorithm) to ensure that resources are allocated in a way that avoids deadlock. Deadlock detection, on the other hand, involves periodically checking the system to see if a deadlock has occurred after it has happened. Deadlock prevention focuses on designing algorithms and protocols in a way that eliminates one of the conditions necessary for deadlock to occur, such as by ensuring that resources are requested in a specific order.
deadlock avoidance
Deadlock is a situation when two thread are waiting on each other to release a resource. Deadlock avoidance methods are : 1) ostrich approach 2) eliminating hold and wait situation 3) eliminating mutual exclusion
Advantage: Deadlock prevention techniques eliminate the possibility of deadlock occurring in a system, ensuring system availability and preventing resource wastage. Disadvantage: Deadlock prevention techniques may lead to reduced system performance or resource utilization, as they often involve overhead in terms of additional checks or restrictions on resource allocation.
Deadlock PreventionDifference from avoidance is that here, the system itself is build in such a way that there are no deadlocks.Make sure atleast one of the 4 deadlock conditions is never satisfied.Deadlock AvoidanceAvoid actions that may lead to a deadlock.Think of it as a state machine moving from 1 state to another as each instruction is executed. moreoverDeadlock detection is a technique to handle deadlocks which tries to find out if the system is in deadlock and then works to recover it from the deadlock if any exists. It is used as an afterthought and is not coordinated with the resource allocating procedures.Deadlock avoidance is a technique which works hand-in-hand with the resource allocation and tries to ensure that a resource request made in a non-deadlocked state is granted only if it will not lead to a deadlock in the future. This technique however makes unrealistic demands about the kind of information it needs from process, in that, it requires the entire pattern of resource requests, past & future.
DEADLOCK PREVENTION:Preventing deadlocks by constraining how requests for resources can be made in the system and how they are handled (system design).The goal is to ensure that at least one of the necessary conditions for deadlock can never hold.DEADLOCK AVOIDANCE:The system dynamically considers every request and decides whether it is safe to grant it at this point,The system requires additional apriori information regarding the overall potential use of each resource for each process.Allows more concurrency.
There are four strategies of dealing with deadlock problem:1. The Ostrich ApproachJust ignore the deadlock problem altogether.2. Deadlock Detection and RecoveryDetect deadlock and, when it occurs, take steps to recover.3. Deadlock AvoidanceAvoid deadlock by careful resource scheduling.4. Deadlock PreventionPrevent deadlock by resource scheduling so as to negate at least one of the four conditions.
The difference is exactly what you have just stated: deadlock prevention is used to stop deadlocks before they happen (to prevent them), while deadlock detection is used to figure out when a process has deadlocked (to detect it).
Yes, deadlock can be resolved by avoiding the conditions that lead to it, breaking the circular wait, or using deadlock prevention techniques like resource allocation graph, timeouts, or priority-based techniques. In some cases, deadlock can also be prevented by ensuring a single thread holds all resources simultaneously or by using a deadlock detection algorithm to preemptively handle it.
The antonym for deadlock is agreement.