ESP32 Forum

Hi,

I would like to know if when we store a value in uint32_t variable it's an atomic operation or not with esp32 ?

How to know which variable type is atomic and which not ?

Hi Cupcake,

Reads and writes will be atomic (the compiler generates 32-bit load and store operations.)

Updating (read/modify/write) is not atomic. You can either use a FreeRTOS "portmux" and critical section to protect access to the variable, or use the standard C atomic API in stdatomic.h to perform an atomic update operation.

Can you confirm if this is the case for memory used by threads on different cores?

If each read/write is atomic, does this apply when each core reads or writes simultaneously?

horace wrote: ↑

Mon Apr 12, 2021 6:29 am

Can you confirm if this is the case for memory used by threads on different cores?

If each read/write is atomic, does this apply when each core reads or writes simultaneously?

Yes, it does. If both cores write to the same 32-bit variable, the value should hold either the value written by one core or the other, not a mix of the two values.

Similarly, if one core reads while the core writes then it should see either the old 32-bit value or the new 32-bit value, not a mix of the two.