How is sleep implemented at the OS level?

by

Sleep() is implemented at the OS level. The processor doesn’t spin when a task/thread/process is sleeping. That particular thread is put on a pending queue (the thread isn’t ready to run) until the time has expired at which point the thread will be placed on the ready to run queue.

In the meantime, other threads that are ready to run will be run.

Only if no threads are ready to run will the OS go into the idle thread, which in generally issues instructions to shutdown (or put into a low-power state anyway) the processor until an hardware interrupt occurs.

Only for a very simple system (like the most simple of embedded systems), might Sleep() actually be implemented as nothing more than a busy wait loop.

Any operating system textbook, such as “Modern Operating Systems” by Tanenbaum will cover this in great detail – pretty much any of them (even an old, cheap, used one).

More Related Contents:

  1. How do I check OS with a preprocessor directive?
  2. Maximum memory which malloc can allocate
  3. stdout thread-safe in C on Linux?
  4. What does fflush(stdin) do in C programing? [duplicate]
  5. Is there an alternative sleep function in C to milliseconds?
  6. Sleep function in Windows, using C
  7. What happens in OS when we dereference a NULL pointer in C?
  8. What is the proper #include for the function ‘sleep()’?
  9. Why are malloc() and printf() said as non-reentrant?
  10. implement time delay in c
  11. How to power down the computer from a freestanding environment?
  12. Understanding concurrent file writes from multiple processes
  13. How to make parent wait for all child processes to finish?
  14. How to use nanosleep() in C? What are `tim.tv_sec` and `tim.tv_nsec`?
  15. What are trade offs for “busy wait” vs “sleep”?
  16. Avoiding the main (entry point) in a C program
  17. Pipe two or more shell commands in C using a loop
  18. how do compilers assign memory addresses to variables?
  19. Non-blocking version of system()
  20. Warning in array of pointers "initialization from incompatible pointer type"
  21. char c[]=”Albus”; printf(“%c”, c); [closed]
  22. Why does GCC use multiplication by a strange number in implementing integer division?
  23. How do you clear the console screen in C?
  24. Determine if char is a num or letter
  25. Difference between char* var; and char *var;? [duplicate]
  26. How to format strings using printf() to get equal length in the output
  27. Is the last comma in C enum required?
  28. C programming: How to program for Unicode?
  29. What are the major differences between ANSI C and K&R C?
  30. Any benefit in using WEXITSTATUS macro in C over division by 256 on exit() status?

Leave a Comment