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Hyeonggon Yoo
hyeyoo
Edited 22 days ago
Reviewing what I learned about Linux context switching years ago because I forgot how it works.
A note for the next time I forget:
Context is switched from one kernel context to another. When a user process is going to be rescheduled, it first switches from user context to its kernel context after storing the registers on the kernel stack (pt_regs) due to a scheduler tick.
When switching between kernel contexts, only callee-saved registers are restored (from cpu_context in thread_struct), as the other registers should have been stored on the kernel stack (by the calling convention) before calling __switch_to()->cpu_switch_to() (on ARM64).
A note for the next time I forget:
Context is switched from one kernel context to another. When a user process is going to be rescheduled, it first switches from user context to its kernel context after storing the registers on the kernel stack (pt_regs) due to a scheduler tick.
When switching between kernel contexts, only callee-saved registers are restored (from cpu_context in thread_struct), as the other registers should have been stored on the kernel stack (by the calling convention) before calling __switch_to()->cpu_switch_to() (on ARM64).
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