Atomic() vs k_sched_lock() vs irq_lock() vs k_mutex_lock()

Kim Bøndergaard

We have an internal discussion about the recommended usage of the 4 methods mentioned in subjects, when the goal is to protect an assignment of a variable (u32 - any platform) within one task so it is not resulting in an invalid reading from a higher priority task.

Mutex'es are usually good since they only disturb the threads being involved in accessing the shared variable - but are they overkill in this case?

irq_lock() sounds like something fast but effects the entire system

k_sched_lock() is fast (according to the manual) but effects all threads as I see it.

atomic is probably a good option, but what's the efficiency on e.g. an ARM platform not natively supporting atomic's.

Any ideas or recommendation about when to use what solution?

Kim Bøndergaard
Prevas A/S
Team Manager / Systems Architect
Hedeager 3, DK-8200 Aarhus N

Phone +45 3315 9090
Mobile +45 5154 3961



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