Operating Systems 2017F Lecture 19

[Notes]

Sample
sample

Additional Notes

Where's main?

• lots of program shave "main" functions - a function that runs first and controls the execution of the program
• Do these have "main" functions?
  • Linux kernel modules
  • FUSE applications?
  • the linux kernel?
  • node web applications?

In many systems, "main" just sets up even handlers

• the event loop can be implicit or explicit
  
  • or there may be no loop at all, just handlers and "interrupts" some kind
    
• event loops poll (check) to see when there are new events
  
• what are event loops for node app?
  
  • where are interrupts for node apps?
    
    • Incoming network requests, it's an event
      

Code run differently in the kernel :

1)functions runs on the bhealf of insmod, unles sit is Independence context

2)codes that run on the bhelaf o the process

3)after an interrupt: no process , it is an interrupt cotext

4) file names : regular programs but the square brackets, execution context + address space. they share the kernel's address space, they are called kernel threads which are independently scheduling . You can not kill them but you can change their scheduling , maybe their priority but not 100%.

does it create a proces? no , but it can create a kernel thread (is it a process? virtual adress space, .
multi- threaded: maintains multiple address processes , ex: fire fox.

ps -elF | less "number" : displayes threads.

OS kernels are essentially the same thing