Re: Deadlock im Recht

Jochen Walerka schrieb:
Arnd Schröter wrote:


Das ist in der Informatik eine Deadlocksituation-eine gegenseitige
Verblockung.


Schön, mal wieder davon zu hören, kenn ich noch aus den Vorlesungen.
Völlig OT:
Kennst du das 5-Philosophen-Problem?



Was ist der Unterschied zwischen Deadlock und Starvation?

Deadlock: Gegenseitiges Blockieren (Zyklus im Wartet-auf-Graphen).

(Zitate aus
http://i30www.ibds.uka.de/teaching/courses/lecture.php?courseid=109&lid=en&termid=13&showmode=allpastterms
)

Conditions for Resource Deadlock

1. Exclusiveness No Sharing at all
! a resource is either assigned to 1 process or is available
2. Hold and Wait Allocating/releasing occur at
! process holding resources can request additional resources
3. No Preemption …from exclusive resources
! previously granted resources cannot forcibly taken away
4. Circular Wait Circular dependency
! must be a circular chain of at least 2 or more processes
! each waiting for resource held by next member of chain
Note: These are not sufficient conditions
Conditions for Resource Deadlock


Starvation: Ein Philosoph verhungert, weil ihm ständig andere
Philosophen vorgezogen werden.

Laut unserer Systemarchitektur-VL sind die Kriterien für eine gültige
Lösung für gegenseitigen Ausschluß:

Four Critical Section Requirements
* Exclusiveness
! At most 1 KLT is in its CS
* Portability
! No assumptions about speed or numbers of CPUs
or scheduling policy
* Progress
! No KLT running outside its CS prevents another
KLT from entering its CS
* Bounded Waiting (no starvation)
! If KLT is waiting on the CS, then this KLT will
eventually enter its CS
! Assumes threads eventually leave their CS


.

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