Why kernel code/thread executing in interrupt context cannot sleep?

by

So what stops the scehduler from putting interrupt context to sleep and taking next schedulable process and passing it the control?

The problem is that the interrupt context is not a process, and therefore cannot be put to sleep.

When an interrupt occurs, the processor saves the registers onto the stack and jumps to the start of the interrupt service routine. This means that when the interrupt handler is running, it is running in the context of the process that was executing when the interrupt occurred. The interrupt is executing on that process’s stack, and when the interrupt handler completes, that process will resume executing.

If you tried to sleep or block inside an interrupt handler, you would wind up not only stopping the interrupt handler, but also the process it interrupted. This could be dangerous, as the interrupt handler has no way of knowing what the interrupted process was doing, or even if it is safe for that process to be suspended.

A simple scenario where things could go wrong would be a deadlock between the interrupt handler and the process it interrupts.

  1. Process1 enters kernel mode.
  2. Process1 acquires LockA.
  3. Interrupt occurs.
  4. ISR starts executing using Process1‘s stack.
  5. ISR tries to acquire LockA.
  6. ISR calls sleep to wait for LockA to be released.

At this point, you have a deadlock. Process1 can’t resume execution until the ISR is done with its stack. But the ISR is blocked waiting for Process1 to release LockA.

More Related Contents:

  1. Image vs zImage vs uImage
  2. adding i2c client devices on x86_64
  3. Linux kernel ARM exception stack init
  4. $(uname -a) returning the same in docker host or any docker container
  5. How do I find ARM Linux entry point when it fails to uncompress?
  6. Context switch internals
  7. How does ARM Linux emulate the dirty, accessed, and file bits of a PTE?
  8. Why does Linux favor 0x7f mappings?
  9. How can Docker run distros with different kernels?
  10. What is the difference between the kernel space and the user space?
  11. Difference between physical/logical/virtual memory address
  12. Adding new driver code to linux source code
  13. module_init() vs. core_initcall() vs. early_initcall()
  14. What is the difference between module_init and subsys_initcall while initializing the driver?
  15. Building kernel uImage using LOADADDR
  16. Handling ARM TrustZones
  17. If threads share the same PID, how can they be identified?
  18. Why am I able to perform floating point operations inside a Linux kernel module?
  19. What are the implications of the linux __user macro?
  20. How to add poll function to the kernel module code?
  21. cat function calling read() infinite times
  22. How to access(if possible) kernel space from user space?
  23. Do Kernel pages get swapped out?
  24. Direct Memory Access in Linux
  25. Linux Stack Sizes
  26. init function invocation of drivers compiled into kernel
  27. How to solve “BUG: scheduling while atomic: swapper /0x00000103/0, CPU#0”? in TSC2007 Driver?
  28. /proc/[pid]/pagemaps and /proc/[pid]/maps | linux
  29. Pass large amount of binary data from u-boot to linux kernel
  30. Sending UDP packets from the Linux Kernel

Leave a Comment