A Dynamic Distributed Algorithm for Read Write Locks

Transcription

1 A Dynamic Distributed Algorithm for Read Write Locks Soumeya Leila Hernane 1,2,3 Jens Gustedt 3 Mohamed Benyettou 1 1 University of Science and Technology of Oran USTO, Algeria 2 Lorraine University, France 3 AlGorille INRIA Grand-Est & LORIA Nancy France inputs/logoinri AlGorille inputs/logoloria 1 /

2 Outline 1 Motivation Mutual exclusion algorithms The bases of Naimi-Trehel Algorithm [5] Concurrency 2 Dynamic Mutual Exclusion Algorithm New requirements Exit strategy 3 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests Departure of readers 4 Current and future work inputs/logoinri AlGorille inputs/logoloria 2 /

3 Outline Motivation 1 Motivation Mutual exclusion algorithms The bases of Naimi-Trehel Algorithm [5] Concurrency 2 Dynamic Mutual Exclusion Algorithm New requirements Exit strategy 3 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests Departure of readers 4 Current and future work inputs/logoinri AlGorille inputs/logoloria 3 /

4 Outline Motivation Mutual exclusion algorithms 1 Motivation Mutual exclusion algorithms The bases of Naimi-Trehel Algorithm [5] Concurrency 2 Dynamic Mutual Exclusion Algorithm New requirements Exit strategy 3 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests Departure of readers 4 Current and future work inputs/logoinri AlGorille inputs/logoloria 4 /

5 Motivation Mutual exclusion algorithms Mutual exclusion algorithms Permission based (Lamport [2], Maekawa [3], Ricart Agrawala [7]) The possession of a token which is passed between nodes ( [4], Raymond [6]). Naimi-Trehel [4] based on path reversal is the benchmark for mutual exclusion. Symbol of critical section Cs inputs/logoinri AlGorille inputs/logoloria 5 /

6 Outline Motivation The bases of Naimi-Trehel Algorithm [5] 1 Motivation Mutual exclusion algorithms The bases of Naimi-Trehel Algorithm [5] Concurrency 2 Dynamic Mutual Exclusion Algorithm New requirements Exit strategy 3 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests Departure of readers 4 Current and future work inputs/logoinri AlGorille inputs/logoloria 6 /

7 Mutual exclusion Motivation The bases of Naimi-Trehel Algorithm [5] Naimi-Trehel Algorithm Logical dynamic tree structure. Root of the tree The last that requested the token. Distributed queue of waiting requests (FIFO strategy) Contributions Allow departure of processes. Include shared token for successive readers. inputs/logoinri AlGorille inputs/logoloria 7 /

8 Mutual exclusion Motivation The bases of Naimi-Trehel Algorithm [5] Naimi-Trehel Algorithm Logical dynamic tree structure. Root of the tree The last that requested the token. Distributed queue of waiting requests (FIFO strategy) Contributions Allow departure of processes. Include shared token for successive readers. inputs/logoinri AlGorille inputs/logoloria 7 /

9 Mutual exclusion Motivation The bases of Naimi-Trehel Algorithm [5] Naimi-Trehel Algorithm Logical dynamic tree structure. Root of the tree The last that requested the token. Distributed queue of waiting requests (FIFO strategy) Contributions Allow departure of processes. Include shared token for successive readers. inputs/logoinri AlGorille inputs/logoloria 7 /

10 Mutual exclusion Motivation The bases of Naimi-Trehel Algorithm [5] Naimi-Trehel Algorithm Logical dynamic tree structure. Root of the tree The last that requested the token. Distributed queue of waiting requests (FIFO strategy) Contributions Allow departure of processes. Include shared token for successive readers. inputs/logoinri AlGorille inputs/logoloria 7 /

11 Outline Motivation Concurrency 1 Motivation Mutual exclusion algorithms The bases of Naimi-Trehel Algorithm [5] Concurrency 2 Dynamic Mutual Exclusion Algorithm New requirements Exit strategy 3 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests Departure of readers 4 Current and future work inputs/logoinri AlGorille inputs/logoloria 8 /

12 Motivation Concurrency Concurrent requests in Naimi-Trehel s Algorithm Initial state inputs/logoinri AlGorille inputs/logoloria 9 /

13 Motivation Concurrency Concurrent requests in Naimi-Trehel s Algorithm p 3 requests the token inputs/logoinri AlGorille inputs/logoloria 9 /

14 Motivation Concurrency Concurrent requests in Naimi-Trehel s Algorithm p 2 and p 5 request the token inputs/logoinri AlGorille inputs/logoloria 9 /

15 Motivation Concurrency Concurrent requests in Naimi-Trehel s Algorithm p 2 and p 5 in transit inputs/logoinri AlGorille inputs/logoloria 9 /

16 Motivation Concurrency Concurrent requests in Naimi-Trehel s Algorithm p 5 in transit inputs/logoinri AlGorille inputs/logoloria 9 /

17 Motivation Concurrency Concurrent requests in Naimi-Trehel s Algorithm Completion of requests inputs/logoinri AlGorille inputs/logoloria 9 /

18 Outline Dynamic Mutual Exclusion Algorithm 1 Motivation Mutual exclusion algorithms The bases of Naimi-Trehel Algorithm [5] Concurrency 2 Dynamic Mutual Exclusion Algorithm New requirements Exit strategy 3 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests Departure of readers 4 Current and future work inputs/logoinri AlGorille inputs/logoloria 10 /

19 Outline Dynamic Mutual Exclusion Algorithm New requirements 1 Motivation Mutual exclusion algorithms The bases of Naimi-Trehel Algorithm [5] Concurrency 2 Dynamic Mutual Exclusion Algorithm New requirements Exit strategy 3 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests Departure of readers 4 Current and future work inputs/logoinri AlGorille inputs/logoloria 11 /

20 Dynamic Mutual Exclusion Algorithm New requirements New requirements New variables {p 1..p i 1, p i..p n } a finite set of processes Waiting queue of received requests Ack, boolean End of request Children, array of processes that have p i as parent Doubly linked Next,Previous list rather than Next chain Avoid overlapping of operations Either p i sends, either it receives request From parent to parent, p i sends request until the root is reached p i browses the same path and sends Ack Average message complexity of O(log(N)). inputs/logoinri AlGorille inputs/logoloria 12 /

21 Dynamic Mutual Exclusion Algorithm New requirements New requirements New variables {p 1..p i 1, p i..p n } a finite set of processes Waiting queue of received requests Ack, boolean End of request Children, array of processes that have p i as parent Doubly linked Next,Previous list rather than Next chain Avoid overlapping of operations Either p i sends, either it receives request From parent to parent, p i sends request until the root is reached p i browses the same path and sends Ack Average message complexity of O(log(N)). inputs/logoinri AlGorille inputs/logoloria 12 /

22 Dynamic Mutual Exclusion Algorithm States for handling requests New requirements Let T=(t 0,..., t n ) an ordered sequence of times with t i < t i+1 referring to requests reception by p i Let T ={..., t i,...} be the set of times of the acknowledgments of those registered requests t 0 < t 0 < t i < t i < t n < t n. Let State(p i, t) be the state of p i at time t SEND = false STATE(p i, t) = Idle REQ = Null WAIT ACK = false inputs/logoinri AlGorille inputs/logoloria 13 /

23 Dynamic Mutual Exclusion Algorithm States for handling requests New requirements Let T=(t 0,..., t n ) an ordered sequence of times with t i < t i+1 referring to requests reception by p i Let T ={..., t i,...} be the set of times of the acknowledgments of those registered requests t 0 < t 0 < t i < t i < t n < t n. Let State(p i, t) be the state of p i at time t SEND = false STATE(p i, t) = Busy REQ Null WAIT ACK = true inputs/logoinri AlGorille inputs/logoloria 13 /

24 Dynamic Mutual Exclusion Algorithm States for handling requests New requirements Let T=(t 0,..., t n ) an ordered sequence of times with t i < t i+1 referring to requests reception by p i Let T ={..., t i,...} be the set of times of the acknowledgments of those registered requests t 0 < t 0 < t i < t i < t n < t n. Let State(p i, t) be the state of p i at time t SEND = true STATE(p i, t) = Sending REQ = Null WAIT ACK = false inputs/logoinri AlGorille inputs/logoloria 13 /

25 Outline Dynamic Mutual Exclusion Algorithm Exit strategy 1 Motivation Mutual exclusion algorithms The bases of Naimi-Trehel Algorithm [5] Concurrency 2 Dynamic Mutual Exclusion Algorithm New requirements Exit strategy 3 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests Departure of readers 4 Current and future work inputs/logoinri AlGorille inputs/logoloria 14 /

26 Departure Dynamic Mutual Exclusion Algorithm Exit strategy Conditions and actions Idle and Queue empty Children Leaving, Sending or Busy waits the its Next and its Previous The doubly linked list Next,Previous is shortcut p i sends either its parent or a new root elected among its children inputs/logoinri AlGorille inputs/logoloria 15 /

27 Dynamic Mutual Exclusion Algorithm Exit strategy New settings for the exit strategy New variables New boolean variables Exit and Leaving p i sets Exit and Leaving to true p i sets Leaving to false STATE(p i, t) = Exiting SEND = false REQ = Null WAIT ACK = false EXIT = true LEAVING = true inputs/logoinri AlGorille inputs/logoloria 16 /

28 Read Write Dynamic Mutual Exclusion Algorithm Outline 1 Motivation Mutual exclusion algorithms The bases of Naimi-Trehel Algorithm [5] Concurrency 2 Dynamic Mutual Exclusion Algorithm New requirements Exit strategy 3 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests Departure of readers 4 Current and future work inputs/logoinri AlGorille inputs/logoloria 17 /

29 Outline Read Write Dynamic Mutual Exclusion Algorithm Read Write requests 1 Motivation Mutual exclusion algorithms The bases of Naimi-Trehel Algorithm [5] Concurrency 2 Dynamic Mutual Exclusion Algorithm New requirements Exit strategy 3 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests Departure of readers 4 Current and future work inputs/logoinri AlGorille inputs/logoloria 18 /

30 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests New requirements for read requests Entering the CS Reading handler, the head of, successive read requesters Request Type, W or R. Next and Previous exchange their types Reader counter incremented by the Reading handler Next writer sets its Previous to the Reading handler inputs/logoinri AlGorille inputs/logoloria 19 /

31 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests New requirements for read requests Entering the CS Reading handler, the head of, successive read requesters Request Type, W or R. Next and Previous exchange their types Reader counter incremented by the Reading handler Next writer sets its Previous to the Reading handler inputs/logoinri AlGorille inputs/logoloria 19 /

32 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests New requirements for read requests Entering the CS Reading handler, the head of, successive read requesters Request Type, W or R. Next and Previous exchange their types Reader counter incremented by the Reading handler Next writer sets its Previous to the Reading handler inputs/logoinri AlGorille inputs/logoloria 19 /

33 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests New requirements for read requests Entering the CS Reading handler, the head of, successive read requesters Request Type, W or R. Next and Previous exchange their types Reader counter incremented by the Reading handler Next writer sets its Previous to the Reading handler 9 8 Cs Cs Cs Cs inputs/logoinri AlGorille inputs/logoloria 19 /

34 Outline Read Write Dynamic Mutual Exclusion Algorithm Departure of readers 1 Motivation Mutual exclusion algorithms The bases of Naimi-Trehel Algorithm [5] Concurrency 2 Dynamic Mutual Exclusion Algorithm New requirements Exit strategy 3 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests Departure of readers 4 Current and future work inputs/logoinri AlGorille inputs/logoloria 20 /

35 Read Write Dynamic Mutual Exclusion Algorithm Departure of readers Other requirements for the dynamicity One reader at once can exit, the Reading handler is informed The Reading handler passes the Reader counter to its Next The Next becomes the new Reading handler The new Reading handler is forwarded to the reader chain p1 old Reading handler p3 new Reading handler inputs/logoinri AlGorille inputs/logoloria 21 /

36 Read Write Dynamic Mutual Exclusion Algorithm Departure of readers Other requirements for the dynamicity One reader at once can exit, the Reading handler is informed The Reading handler passes the Reader counter to its Next The Next becomes the new Reading handler The new Reading handler is forwarded to the reader chain p1 old Reading handler p3 new Reading handler inputs/logoinri AlGorille inputs/logoloria 21 /

37 Outline Current and future work 1 Motivation Mutual exclusion algorithms The bases of Naimi-Trehel Algorithm [5] Concurrency 2 Dynamic Mutual Exclusion Algorithm New requirements Exit strategy 3 Read Write Dynamic Mutual Exclusion Algorithm Read Write requests Departure of readers 4 Current and future work inputs/logoinri AlGorille inputs/logoloria 22 /

38 Current and future work Current and future work The proof of Safety and liveness properties Include our extended Algorithm to the DHO API [1] Provide an efficient management for locking and mapping data (and subranges of it) Undertake experiments of that model Simulated mode(gras API of SimGrid [8]) Large scale platform(grid inputs/logoinri AlGorille inputs/logoloria /

39 Current and future work Soumeya Hernane, Leila, Jens Gustedt, and Mohamed Benyettou. Modeling and Experimental Validation of the Data Handover API. In Jukko Riekki, Mika Ylianttila, and Minyi Guo, editors, Advances in Grid and Pervasive Computing, volume 6646 of LNCS, pages , Oulu, Finland, May Springer. Leslie Lamport. Ti clocks, and the ordering of events in a distributed system. Commun. ACM, 21: , July Mamoru Maekawa. An algorithm for mutual exclusion in decentralized systems. ACM Trans. Comput. Syst., 3: , May Mohamed Naimi and Michel Trehel. How to detect a failure and regenerate the token in the log(n) distributed algorithm for mutual exclusion. In Proceedings of the 2nd International Workshop on Distributed Algorithms, pages , London, UK, Springer-Verlag. inputs/logoinri AlGorille inputs/logoloria /

40 Current and future work Mohamed Naimi, Michel Trehel, and André Arnold. A log(n) distributed mutual exclusion algorithm based on path reversal. J. Parallel Distrib. Comput., 34:1 13, April Kerry Raymond. A tree-based algorithm for distributed mutual exclusion. ACM Transactions on Computer Systems, 7:61 77, Glenn Ricart and Ashok K. Agrawala. An optimal algorithm for mutual exclusion in computer networks. Commun. ACM, 24:9 17, January Pedro Velho and Arnaud Legrand. Accuracy study and improvement of network simulation in the SimGrid framework. In Simutools 09, pages 1 10, Brussels, Belgium, ICST. inputs/logoinri AlGorille inputs/logoloria /