Understanding Signal Handling in Operating Systems: A Deep Dive into Processes A and B - P, Study Guides, Projects, Research of Operating Systems

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Project 2 Roadmap++

Awwww! ugly slides.

HANDLING BBBBBBBBBBBBBB…..

Review

Process A main() { for(1000) Print “A” Kill(B, SIGUSR1) } Process B function handler() { Print “HANDLING” } main() { Signal(&handler, SIGUSR1) for(;;) Print “B” } AABBAABBAABB……… 1000 A’S

Output

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

HANDLING BBBBBBBBBBBBBB…..

Review

Process A main() { for(1000) Print “A” Kill(B, SIGUSR1) } Process B function handler() { Print “HANDLING” } main() { Signal(&handler, SIGUSR1) for(;;) Print “B” } AABBAABBAABB……… 1000 A’S Output

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

Executed by stub code once a signal has been handled

Helper Functions

 Send_Signal

 Set_Handler

 Check_Pending_Signal

 Setup_Frame

 Complete_Handler

Overview

A B

Overview

A B

RegDeliver RegDeliver Signal(SIGCHILD) Signal(SIGCHILD, ….)

Scheduler: w/o signals

A

scheduler B

B

src/geekos/lowlevel.asm

Scheduler: w/ signals

A

B’s user level sig. hand.

B

scheduler B

Check Pending Signal

 Boolean output  Determines whether to proceed with signal handling

Scheduler: w/ signals

A

B’s user level sig. hand.

B

scheduler B Check Pending Signal true false

Setup Frame

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

Scheduler: w/ signals

A

B’s user level sig. hand.

B

scheduler B Check Pending Signal Setup Frame