1. Deadlock Detection in
Distributed Systems
Dr. Davarpanah
Research:
Kaywan Zayer
Reza Ramezani
Mohammad Khosravi

2. Deadlock
• Introduction
• Strategies to handle deadlock
– Ostrich algorithm (ignore it)
– Detection (let occur, detect, recover)
– Prevention (make it impossible to occur)
– Avoidance (careful resource allocation)

3. Deadlock Detection
• Centralized
– Single point of failure
– bottleneck
• Distributed
– Soojung Lee
– Monjurul Alom et al
– Farajzadeh et al

4. Introduction
• Process dependency
– wait-for graph (WFG)
• Request model
– AND
– OR
– p out-of q
• Communication model
– Just message communication
– Bounded delay, reliable protocol

5. Soojung Lee
• Dependency Model
– Reduced wait-for graph (RWFG)
– knot
• Request model
– OR
• Blocked process can participate in deadlock
detection algorithm

6. Message
• Probe
– Distributed Spanning Tree (DST)
– Path-string decoding
– Unique id
• Reply
– ACTIVE
– REPORT

7. Example
(i) WFG (ii) DST

8. Example
(iii) RWFG after receive ACTIVE
(iv) RWFG after receive REPORT
(v) Final RWFG

9. Monjurul Alom et al
• Distributed Database System
• Dependency model
– Transaction wait-for graph (TWFG)
• Request model
– AND
• Linear Transaction Structure (LTS)
• Distributed Transaction Structure (DTS)

10. Algorithm Scheme
• LTS for each local site
• DTS for global resource transaction
communication
• Priority Id for each transaction in each of the
sites
• The local and global cycles
• Abort of the victim transaction based on the
cycles

11. Example
TWFG

12. Example
LTS2 : {3->5, 5->6, 6->3}
{7->10, 10->9, 9->7}
{10->9, 9->11, 11->10}
LTS3 :

13. Example

14. Example
DTS1 : {4->3, 3->3, 3->4, 4->4} DTS2 : {6->4, 4->8, 8->7, 7->6}

15. Detected deadlock, breaking it

16. Final TWFG

17. Farajzadeh et al
• History-based edge chasing
– Probe message
• Request model
– p out-of q
• Messages
– Probe
– Clean-up
– Ok
– Deny

18. Algorithm
• Receive probe
– In memory and id = received id
• Prefix of received route-string
– deadlock
• Otherwise
– Save probe with smaller path-string and propagate received
probe
• Deadlock
– Initiator
• Clean-up and suicide
– Otherwise
• Request permission for suicide

20. Comparison
• First an third algorithm
– Both use probe messages
– Build WFG
– Different in message number, delay, message size
and resolution scheme
Sujung lee farajzadeh
Number of
message
2e <=e
Message size d+2 <=O(d)
delay O(dlogn) n
resolutaion yes Yes, 2 message
e : number of edge in WFG, n : number of node, d : diameter of WFG