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Chapter_4_-_Synchronization

Chapter_4_-_Synchronization - 4 Synchronization and...

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4 Process Synchronization 1 4 Synchronization and Interprocess Communication Further reading: Stallings Chapter 5 Silberschatz Chapter 6 Tanenbaum Chapter 2.3 Operating Systems
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4 Process Synchronization 2 Needs of Processes Allocation of processor time Allocation and sharing resources Communication among processes Synchronization of multiple processes Operating Systems
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4 Process Synchronization 3 How can processes/threads exchange information shared memory need to establish a region of shared memory usually resides in the address space of a process shared memory systems system calls are only needed to setup the memory Basic operations: read/write message passing send messages between processes requires system calls to the OS for every message often easier to realize for networked process communication – send/receive Operating Systems
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Shared Memory Uniprocessor architecture and SMPs Common Address Space to Physical Memory by hardware Operating must provide appropriate memory management to processes or threads Threads share resources within a process Processes can share memory on shared memory segments Can establish also shared memory for loosely coupled systems Provide special middleware NUMA Distributed System Architectures Performance depends System bus Network characteristics 4 Process Synchronization 4 P Q Middleware Middleware OS Communica tion Layer Physical Layer Read/Write Address OS Communica tion Layer Physical Layer Channel / Bus / Network Operating Systems
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4 Process Synchronization 5 Message Passing No sharing of resources between processes needed basic operations: send (destination, message): send a message receive (source,message): receive a message Send/receive can be blocking non-blocking Blocking send + blocking receive tight coupling between processes Non blocking send + blocking receive Operating Systems
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4 Process Synchronization 6 Direct communication Direct symmetric communication Each process that wants to communicate must name the recipient: send (P, message) send a message to process P receive (Q, message) receive a message from process Q Communication link established automatically link associated exactly between two processes Direct asymmetric communication Use instead send (P, message) send a message to process P receive (message) receive message from arbitrary process Operating Systems
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4 Process Synchronization 7 Indirect communication Problem of Direct Addressing changing a process identifier may impact all other process definitions limited modularity Indirect addressing uses mailbox or port concept Mailbox: Shared by multiple receiver Port: Receiver Specific, e.g. WebServer uses port 80 send (A, message) send a message to mailbox/port named A receive (A, message) receive a message from mailbox A link is only established if both members share a mailbox Operating Systems
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4 Process Synchronization 8 One-to-One private communication link between two processes Operating Systems
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4 Process Synchronization 9 Many-to-one Client server interactions Operating Systems
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