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In order to synchronize with C or external memory, atomic operations over raw pointers are need. Although there is already an `Atomic::from_ptr()` to provide a `&Atomic<T>`, it's more convenient to have helpers that directly perform atomic operations on raw pointers. Hence a few are added, which are basically an `Atomic::from_ptr().op()` wrapper. Note: for naming, since `atomic_xchg()` and `atomic_cmpxchg()` have a conflict naming to 32bit C atomic xchg/cmpxchg, hence the helpers are just named as `xchg()` and `cmpxchg()`. For `atomic_load()` and `atomic_store()`, their 32bit C counterparts are `atomic_read()` and `atomic_set()`, so keep the `atomic_` prefix. [boqun: Fix typo spotted by Alice and fix broken sentence spotted by Gary] Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Gary Guo <gary@garyguo.net> Link: https://patch.msgid.link/20260120115207.55318-3-boqun.feng@gmail.com Link: https://patch.msgid.link/20260303201701.12204-11-boqun@kernel.org