为什么我们同时拥有 __atomic_store_n 和 __atomic_store

Question

I am working on a simple linux driver and I am trying to understand how the atomic built-ins for the gcc compiler work and how they optimize performance. My question is: why do we need both __atomic_store and __atomic_store_n ? What is their difference?

Answer 1

look at gcc manual for the difference between the two atomic_store functions

https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html

Built-in Function: void __atomic_store_n (type *ptr, type val, int memorder)

This built-in function implements an atomic store operation. It writes val into *ptr.

The valid memory order variants are __ATOMIC_RELAXED, __ATOMIC_SEQ_CST, and __ATOMIC_RELEASE.

Built-in Function: void __atomic_store (type *ptr, type *val, int memorder)

This is the generic version of an atomic store. It stores the value of *val into *ptr.

the __atomic.._n methods can be used for any integer scalar or pointer with a size of 1, 2, 4, or 8 bytes, instead the generic version is applicable to any data type.