// SPDX-License-Identifier: GPL-2.0 //! Memory barriers.//!//! These primitives have the same semantics as their C counterparts: and the precise definitions//! of semantics can be found at [`LKMM`].//!//! [`LKMM`]: srctree/tools/memory-model/ /// A compiler barrier.////// A barrier that prevents compiler from reordering memory accesses across the barrier.#[inline(always)]pub(crate) fn barrier() {    // By default, Rust inline asms are treated as being able to access any memory or flags, hence    // it suffices as a compiler barrier.    //    // SAFETY: An empty asm block.    unsafe { core::arch::asm!("") };} /// A full memory barrier.////// A barrier that prevents compiler and CPU from reordering memory accesses across the barrier.#[inline(always)]pub fn smp_mb() {    if cfg!(CONFIG_SMP) {        // SAFETY: `smp_mb()` is safe to call.        unsafe { bindings::smp_mb() };    } else {        barrier();    }} /// A write-write memory barrier.////// A barrier that prevents compiler and CPU from reordering memory write accesses across the/// barrier.#[inline(always)]pub fn smp_wmb() {    if cfg!(CONFIG_SMP) {        // SAFETY: `smp_wmb()` is safe to call.        unsafe { bindings::smp_wmb() };    } else {        barrier();    }} /// A read-read memory barrier.////// A barrier that prevents compiler and CPU from reordering memory read accesses across the/// barrier.#[inline(always)]pub fn smp_rmb() {    if cfg!(CONFIG_SMP) {        // SAFETY: `smp_rmb()` is safe to call.        unsafe { bindings::smp_rmb() };    } else {        barrier();    }}