Matakuliah
Tahun
Versi/Revisi
: T0316/sistem Operasi
: 2005
:5
Pertemuan 6
Komunikasi antar Proses (IPC)
Lanjutan
OFFCLASS01
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• menerangkan interprocess communication
tanpa busy waiting (C2)
2
Outline Materi
Semaphore
Mutexes
Monitor
Message Passing
3
INTERPROCESS COMMUNICATION (Cont’d)
SEMAPHORES
- Integer variable to count the number of wakeups
- It is 0 if there is no wakeup, or some positive value if one or
more wakeups were pending
Two operations on semaphore:
1.
DOWN (S)
S=S–1
Or
alternatively
1.
IF (S < 0) THEN SLEEP
2.
DOWN (S)
IF (S > 0) THEN S = S – 1
ELSE SLEEP
UP (S)
S=S+1
IF (S <= 0) THEN WAKEUP
Operation DOWN and UP are Atomic Action
4
The producer-consumer problem
using semaphores
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MUTEXES
- Variable that can be one of two states:
unlocked or locked
Implementation of mutex_lock and mutex_unlock
6
MONITORS
- Higher level synchronization
primitives
- A collection of procedure,
variables and data structure that
are all packed together into a
module
A monitor
7
Producer-consumer problem using monitors
- Only one monitor procedure can be active at a time
- Buffer has N slots
8
MESSAGE PASSING
Two primitives:
- Send (destination, &message)
- Receive (source, &message)
Design issues for message passing system
- Message lost
- Acknowledgement
- Domains
- Authentication
- Performance
9
Implementation of producerconsumer problem using
message passing
10
Several variants of message passing:
- Mailbox
 Buffering mechanism
- Rendezvous
 No buffering mechanism
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