kernel: O(1) search for threads among CPUs #101372
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Instead of performing a linear search to determine if a given thread is running on another CPU, or if it is marked as being preempted by a metaIRQ on any CPU do this in O(1) time. On SMP systems, Zephyr already tracks the CPU on which a thread executes (or lasted executed). This information is leveraged to do the search in O(1) time. Signed-off-by: Peter Mitsis <[email protected]>
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TaiJuWu
reviewed
Dec 20, 2025
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| #ifdef CONFIG_SMP | ||
| thread_base->is_idle = 0; | ||
| thread_base->cpu = 0; |
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It means the run on cpu 0 last time, should we use a magic number to indicate edge case for thread does not run before?
Additional, there is comment from _thread_base, the semantic is changed now.
/* CPU index on which thread was last run */
uint8_t cpu;
By the way, I think it is used to cpu affinity before but I am not sure we have this feature or not.
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Instead of performing a linear search to determine if a given thread is running on another CPU, or if it is marked as being preempted by a metaIRQ on any CPU do this in O(1) time.
On SMP systems, Zephyr already tracks the CPU on which a thread executes (or lasted executed). This information is leveraged to do the search in O(1) time.