Transcript Implementing Processes, Threads, and Resources

Slide 5-1
Device
Management
Copyright © 2004 Pearson Education, Inc.
5
Operating Systems: A Modern Perspective, Chapter 5
Announcements
• Homework Set #1 due Thursday 11 am, see
moodle
• copyright issues with lectures
• Program Assignment #1 coming soon
• Read chapters 4 and 5
– skip sections 4.7, 4.8
– skip Sections 5.4, 5.5 for now
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
Slide 5-2
Slide 5-3
Determining When I/O is Complete
CPU
Interrupt Pending
Device
Device
Device
• CPU incorporates an “interrupt pending” flag
• When device.busy  FALSE, interrupt pending flag is set
• Hardware “tells” OS that the interrupt occurred
• Interrupt handler part of the OS makes process ready to run
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
Slide 5-4
Control Unit with Interrupt
(Hardware)
PC = <machine start address>;
IR = memory[PC];
haltFlag = CLEAR;
while(haltFlag not SET) {
execute(IR);
PC = PC + sizeof(INSTRUCT);
IR = memory[PC];
if(InterruptRequest) {
memory[0] = PC;
PC = memory[1]
};
could
be a
trap
instr.
memory[1] contains the address of the interrupt handler
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
Examples of Exceptions in Pentium
Systems
Slide 5-5
Class
Cause
Async/
Sync
Return
behavior
Trap
Intentional
exception
Sync
Fault
Potentially
recoverable
error
nonrecoverable error
signal from I/O
device
Sync
always returns
to next
instruction
might return to
current
instruction
never returns
Abort
Interrupt
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Sync
Async
Operating Systems: A Modern Perspective, Chapter 5
always returns
to next
instruction
The Trap Instruction Operation
Mode
Slide 5-6
a trap is a
“software” interrupt
S
Branch Table
1
2
trap
3
Trusted
Code
User
Supervisorhardware interrupts behave similarly,
an interrupt gives an offset into
interrupt vector table
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
Examples of Exceptions in Pentium
Systems
Slide 5-7
Exception Table, also called Branch Table or
Jump Table or Interrupt Vector
Exception
Number
Description
Exception Class
0
Divide error
fault
13
General
protection fault
fault
14
Page fault
fault
18
machine check
abort
32-127
OS-defined
Interrupt or trap
OS
assigns
128
System call
Trap
129-255
OS-defined
Interrupt or trap
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
nonmaskable
maskable
interrupts
Maskable Interrupts
Slide 5-8
• Maskable interrupts can be turned off by CPU
before execution of critical instruction sequences
– are used by device controllers to talk with CPU
• Nonmaskable interrupts/exceptions is reserved for
events such as unrecoverable memory errors and
cannot be turned off by the CPU
• Can have multiple interrupt priority levels
– high-priority interrupts can preempt execution of a lowpriority interrupt
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Operating Systems: A Modern Perspective, Chapter 5
Disabling Maskable Interrupts
Slide 5-9
saveProcessorState() {
for(i=0; i<NumberOfRegisters; i++)
memory[K+i] = R[i];
for(i=0; i<NumberOfStatusRegisters; i++)
memory[K+NumberOfRegisters+i] = StatusRegister[i];
}
PC = <machine start address>;
IR = memory[PC];
haltFlag = CLEAR;
while(haltFlag not SET) {
execute(IR);
PC = PC + sizeof(INSTRUCT);
IR = memory[PC];
if(InterruptRequest && InterruptEnabled) {
disableInterupts();
memory[0] = PC;
have to reenable
PC = memory[1]
};
interrupts after done
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
Classes of System Calls Invoked by
trap
system call interface
Information CommManagement unications
Process
File
Device
control Management Management
•
•
•
•
•
•
•
end, abort
load, execute
create, terminate
get attributes, set
wait for time
wait event, signal event
allocate memory, free
•
•
•
•
•
•
•
•
request device, release
read, write, reposition
get attributes, set
logically attach or
detach devices
Note
Similarity
create, delete
open, close
read, write, reposition
get attributes, set
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•
•
•
Slide 5-10
•
•
•
•
create connection,
delete
send messages, receive
transfer status info
attach remote devices,
detach
get time/date, set
get system data, set
get process, file, or
device attributes, set
Operating Systems: A Modern Perspective, Chapter 5
The Device Driver Interface
…
write(…);
…
Device Interface
Terminal
Driver
Printer
Driver
Disk
Driver
Terminal
Controller
Printer
Controller
Disk
Controller
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Operating Systems: A Modern Perspective, Chapter 5
Slide 5-11
Slide 5-12
Device Management Organization
Application
Process
System Interface
e.g. write()
File
Manager
Device-Independent
Device-Dependent
Device Manager
or I/O Subsystem
Hardware Interface
drivers
Command
Status
Data
Device Controller
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
Device System Call Interface
Slide 5-13
• Functions available to application programs
• Abstract all devices (and files) to a few interfaces
• Make interfaces as similar as possible
– Block vs character
– Sequential vs direct/random access
– Blocking versus Non-Blocking I/O
• blocking system call: process put on wait queue until I/O completes
• non-blocking system call: returns immediately with partial number of
bytes transferred, e.g. keyboard, mouse, network sockets
– Synchronous versus asynchronous
• asynchronous returns immediately, but at some later time, the full
number of bytes requested is transferred
• Device driver implements functions (one entry point per
API function)
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
Example: BSD UNIX Driver
open
close
ioctl
read
write
strategy
select
stop
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Prepare dev for operation
No longer using the device
Character dev specific info
Character dev input op
Character dev output op
Block dev input/output ops
Character dev check for data
Discontinue a stream output op
Operating Systems: A Modern Perspective, Chapter 5
Slide 5-14
Device Independent Function Call
Trap Table
funci(…)
dev_func_i(devID, …) {
// Processing common to all devices
…
switch(devID) {
case dev0: dev0_func_i(…);
break;
case dev1: dev1_func_i(…);
break;
…
case devM: devM_func_i(…);
break;
};
// Processing common to all devices
…
}
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
Slide 5-15
Overlapping the Operation of a
Device and the CPU
. . .
read(dev_I, “%d”, x);
y = f(x)
. . .
. . .
startRead(dev_I, “%d”, x);
. . .
While(stillReading()) ;
y = f(x)
. . .
Data on device
Variable x
Register
Memory
CPU
Device dev_I
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Slide 5-16
Operating Systems: A Modern Perspective, Chapter 5
Overlapping CPU-Controller
Operations in a Process
Slide 5-17
could be non-blocking or asynchronous
system call
App
I/O Ctlr
t1
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t2 t3 t4
t5
t6
t7
Operating Systems: A Modern Perspective, Chapter 5
t8
t9
Overlapping Processing and I/O
App1 makes a blocking or synchronous
system call
App 1
App 2
I/O Ctlr
t1
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t2
t3
Operating Systems: A Modern Perspective, Chapter 5
t4
Slide 5-18
Device Manager I/O Strategies
Slide 5-19
• Underneath the blocking/non-blocking
synchronous/asynchronous system call API,
OS can implement several strategies for I/O
with devices
– direct I/O with polling
– direct I/O with interrupts
– DMA with interrupts
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
Polling I/O Read Operation
read(device, …);
1
System Interface
Data
read driver
5
write driver
2
3
4
Hardware Interface
Command
Status
Data
Device Controller
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
Slide 5-20
Interrupt-driven I/O Operation
read(device, …);
1
Slide 5-21
9
8b
Data
System Interface
Device Status Table
4
read driver
2
7
Device
Handler
write driver
6
3
Interrupt
Handler
5
Hardware Interface
Command
Status
Data
Device Controller
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
8a
Driver-Kernel Interface
Slide 5-22
• Drivers are distinct from main part of kernel
• Kernel makes calls on specific functions,
drivers implement them
• Drivers use kernel functions for:
–
–
–
–
Device allocation
Resource (e.g., memory) allocation
Scheduling
etc. (varies from OS to OS)
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
DMA with Interrupts Example
1. device driver told
to transfer bytes from
disk to memory
2. dev driver informs
disk controller
5. DMA
sends each DMA/bus/interrupt
Controller
byte to
memory
6. DMA
interrupts
CPU when
done
Copyright © 2004 Pearson Education, Inc.
Slide 5-23
CPU
CPU/Memory Bus
Memory
I/O Bus
3. disk controller
initiates DMA
Disk
Controller 4. disk controller sends
each byte to DMA
controller
Operating Systems: A Modern Perspective, Chapter 5
Handling Interrupts
Device driver J
int read(…) {
// Prepare for I/O
save_state(J);
out dev#
// Done (no return)
}
Device status table
J
Device interrupt handler J
void dev_handler(…) {
get_state(J);
//Cleanup after op
signal(dev[j]);
return_from_sys_call();
}
Interrupt Handler
Device Controller
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Slide 5-24
Operating Systems: A Modern Perspective, Chapter 5
Handling Interrupts(2)
Device driver J
Device interrupt handler J
int read(…) {
…
out dev#
// Return after interrupt
wait(dev[J});
return_from_sys_call();
}
void dev_handler(…) {
//Cleanup after op
signal(dev[j]);
}
Interrupt Handler
Device Controller
Copyright © 2004 Pearson Education, Inc.
Operating Systems: A Modern Perspective, Chapter 5
Slide 5-25