Project 2 Roadmap

1
Project 2 Roadmap
2
Review
Process B function handler() Print
HANDLING main() Signal(handler,
SIGUSR1) for() Print B

• Process A
• main()
• for(1000)
• Print A
• Kill(B, SIGUSR1)

Output
HANDLING
BBBBBBBBBBBBBB..
AABBAABBAABB
3
System Calls

• Sys_Signal register a signal handler
• Sys_Kill send a signal
• Sys_RegDeliver initialize signal handling for a
  process
• Sys_WaitNoPID wait for any child process to die
• Sys_ReturnSignal indicate completion of signal
  handler

4
System Calls

• Sys_Signal register a signal handler
• Sys_Kill send a signal
• Sys_RegDeliver initialize signal handling for a
  process
• Sys_WaitNoPID wait for any child process to die
• Sys_ReturnSignal indicate completion of signal
  handler

Referenced in user code
5
Review
Process B function handler() Print
HANDLING main() Signal(handler,
SIGUSR1) for() Print B

• Process A
• main()
• for(1000)
• Print A
• Kill(B, SIGUSR1)

Output
HANDLING
BBBBBBBBBBBBBB..
AABBAABBAABB
6
System Calls

• Sys_Signal register a signal handler
• Sys_Kill send a signal
• Sys_RegDeliver initialize signal handling for a
  process
• Sys_WaitNoPID wait for any child process to die
• Sys_ReturnSignal indicate completion of signal
  handler

7
System Calls

• Sys_Signal register a signal handler
• Sys_Kill send a signal
• Sys_RegDeliver initialize signal handling for a
  process
• Sys_WaitNoPID wait for any child process to die
• Sys_ReturnSignal indicate completion of signal
  handler

8
Helper Functions

• Send_Signal
• Set_Handler
• Check_Pending_Signal
• Setup_Frame
• Complete_Handler

9
Review
Process B function handler() Print
HANDLING main() Signal(handler,
SIGUSR1) for() Print B

• Process A
• main()
• for(1000)
• Print A
• Kill(B, SIGUSR1)

10
Overview
A
B
11
Overview
A
B
RegDeliver
RegDeliver
Signal(SIGCHILD)
Signal(SIGCHILD, .)
12
Overview
libc
A
B
RegDeliver
RegDeliver
Signal(SIGCHILD)
Signal(SIGCHILD, .)
13
Overview
libc
A
B
RegDeliver
RegDeliver
Signal(SIGCHILD)
Signal(SIGCHILD, .)
Set_handler
flag pointer
SIGCHILD
SIGUSR1
SIGUSR2
KILL

14
Overview
libc
A
B
RegDeliver
RegDeliver
Signal(SIGCHILD)
Signal(SIGCHILD, .)
Set_handler
flag pointer
SIGCHILD
SIGUSR1
SIGUSR2
KILL

15
Overview
flag pointer
SIGCHILD
SIGUSR1
SIGUSR2
KILL

Send_signal
16
Overview
flag pointer
SIGCHILD
SIGUSR1 X
SIGUSR2
KILL

Send_signal
17
Overview
flag pointer
SIGCHILD
SIGUSR1 X
SIGUSR2
KILL

18
Helper Functions

• Send_Signal
• Set_Handler
• Check_Pending_Signal
• Setup_Frame
• Complete_Handler
• Look at Scheduler

19
Scheduler w/o signals
scheduler
A
B
src/geekos/lowlevel.asm
20
Scheduler w/ signals
scheduler
Bs user level sig. hand.
B
21
Scheduler w/ signals
Check Pending Signal
scheduler
Bs user level sig. hand.
B
22
Check Pending Signal

• Boolean output
• Determines whether to proceed with signal handling

23
Scheduler w/ signals
Check Pending Signal
scheduler
Bs user level sig. hand.
B
24
Scheduler w/ signals
Check Pending Signal
Setup Frame
scheduler
Bs user level sig. hand.
B
25
Setup Frame

• Sets up state to enable user-level handling code
  execution

26
Scheduler w/ signals
Check Pending Signal
Setup Frame
scheduler
Bs user level sig. hand.
B
27
Setup Frame

• Sets up state to enable user-level handling code
  execution
• How are function called?

28
Function Calls

• Parameter of return address is stored on the
  stack so when finished
• Pop off stack
• Continue execution
• Setup Frame
• Enables user stack to keep
• Interrupt_State Vector
• Return address

29
Storing Return Address

• Want complete_handler to execute once user level
  handling done.
• Hack
• Place address of return_signal as return address
  on stack
• Now return_signal stred as function

30
Scheduler w/ signals
Check Pending Signal
Setup Frame
scheduler
CompleteHandler
Bs user level sig. hand.
B