FIGURE 4

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CIS 630 OPERATING SYSTEMS
CHAPTER 4 Morty Kwestel 2003
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CHAPTER 4

• Kernel
• Queues
• Resources
• Implementation
• Threads
• Implementation

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CHAPTER 4

• Processes
• Descriptors
• Operations
• Synchronization
• Semaphores
• Monitors
• Clocks

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CHAPTER 4

• Communication
• Message passing
• Interrupts

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FIGURE 4-1
? O/S Process for Login
?Parent
?Child
?Grandchild
Process Creation hierarchy
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FIGURE 4-3(a)
Priority Queue
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FIGURE 4-3(b c)
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FIGURE 4-4
Threads within a Process
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FIGURE 4-5
Structure of PCB
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FIGURE 4-6
Process Status changes
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Request
Request(resource) if (Free(resource)) Allo
cate(resource, self) else Block(self,
resource) Scheduler()
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Release
Release(resource) Deallocate(resource,
self) if(process_blocked_on(resource,
process)) Allocate(resource, process)
Unblock((process, resource)
Scheduler()
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Test Set
TS(R, X) R X // TEST R holds previous
value of X. X 0 // SET value of X is
always reset to 0. R is a CPU Register. X
is a location in Memory that will hold a Boolean
value.
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Semaphore
wait(s) signal(s) if (s 1)
s s 0 else busy wait
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Semaphore / TS
wait(s) do TS(R, s) while (!R) // busy
wait if R 0. signal(s)s 1
//where s X.
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Monitor
wait(mutex) //body of procedure if(urgen
t_count) signal(urgent) else signal(mutex
)
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Wait Condition
cond_count if (urgent_count)
signal(urgent) else signal(mutex) wait(cond
_X) cond_count--
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Signal Condition
if (cond_count) urgent_count
signal(cond_X) wait(urgent)
urgent_count--
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Timer
int delay_sem 0   Delay(tdel) Set_T
imer(tdel) wait(delay_sem) Time-Out()
signal(delay_sem)
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Functions
tn Create_LTimer()   Destroy_Timer(tn)
Set_Timer(tn, tdel)
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FIGURE 4-8
?Priority based
Insert
Timer Queue Absolute differences
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Set Timer
Set_Ltimer(tn, tdel) wnew Get_Time()
tdel wold head(TQ)-gtwakeup if (wnew
lt wold) Set_Timer(tdel)
insert(TQ, (p, tn, wnew))
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FIGURE 4-9
Timer Queue Relative difference
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FIGURE 4-10a
m holds address of buffer
Send/Receive buffers Copying
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FIGURE 4-10b
Send/Receive buffers Copying
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FIGURE 4-10c
Send/Receive buffers Copying
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FIGURE 4-11a
Basic interrupt
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FIGURE 4-11b
Monitor interrupt