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Diffstat (limited to 'include/asm-generic/barrier.h')
| -rw-r--r-- | include/asm-generic/barrier.h | 255 |
1 files changed, 255 insertions, 0 deletions
diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h new file mode 100644 index 000000000..640f09479 --- /dev/null +++ b/include/asm-generic/barrier.h @@ -0,0 +1,255 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * Generic barrier definitions. + * + * It should be possible to use these on really simple architectures, + * but it serves more as a starting point for new ports. + * + * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ +#ifndef __ASM_GENERIC_BARRIER_H +#define __ASM_GENERIC_BARRIER_H + +#ifndef __ASSEMBLY__ + +#include <linux/compiler.h> +#include <asm/rwonce.h> + +#ifndef nop +#define nop() asm volatile ("nop") +#endif + +/* + * Force strict CPU ordering. And yes, this is required on UP too when we're + * talking to devices. + * + * Fall back to compiler barriers if nothing better is provided. + */ + +#ifndef mb +#define mb() barrier() +#endif + +#ifndef rmb +#define rmb() mb() +#endif + +#ifndef wmb +#define wmb() mb() +#endif + +#ifndef dma_rmb +#define dma_rmb() rmb() +#endif + +#ifndef dma_wmb +#define dma_wmb() wmb() +#endif + +#ifndef __smp_mb +#define __smp_mb() mb() +#endif + +#ifndef __smp_rmb +#define __smp_rmb() rmb() +#endif + +#ifndef __smp_wmb +#define __smp_wmb() wmb() +#endif + +#ifdef CONFIG_SMP + +#ifndef smp_mb +#define smp_mb() __smp_mb() +#endif + +#ifndef smp_rmb +#define smp_rmb() __smp_rmb() +#endif + +#ifndef smp_wmb +#define smp_wmb() __smp_wmb() +#endif + +#else /* !CONFIG_SMP */ + +#ifndef smp_mb +#define smp_mb() barrier() +#endif + +#ifndef smp_rmb +#define smp_rmb() barrier() +#endif + +#ifndef smp_wmb +#define smp_wmb() barrier() +#endif + +#endif /* CONFIG_SMP */ + +#ifndef __smp_store_mb +#define __smp_store_mb(var, value) do { WRITE_ONCE(var, value); __smp_mb(); } while (0) +#endif + +#ifndef __smp_mb__before_atomic +#define __smp_mb__before_atomic() __smp_mb() +#endif + +#ifndef __smp_mb__after_atomic +#define __smp_mb__after_atomic() __smp_mb() +#endif + +#ifndef __smp_store_release +#define __smp_store_release(p, v) \ +do { \ + compiletime_assert_atomic_type(*p); \ + __smp_mb(); \ + WRITE_ONCE(*p, v); \ +} while (0) +#endif + +#ifndef __smp_load_acquire +#define __smp_load_acquire(p) \ +({ \ + __unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p); \ + compiletime_assert_atomic_type(*p); \ + __smp_mb(); \ + (typeof(*p))___p1; \ +}) +#endif + +#ifdef CONFIG_SMP + +#ifndef smp_store_mb +#define smp_store_mb(var, value) __smp_store_mb(var, value) +#endif + +#ifndef smp_mb__before_atomic +#define smp_mb__before_atomic() __smp_mb__before_atomic() +#endif + +#ifndef smp_mb__after_atomic +#define smp_mb__after_atomic() __smp_mb__after_atomic() +#endif + +#ifndef smp_store_release +#define smp_store_release(p, v) __smp_store_release(p, v) +#endif + +#ifndef smp_load_acquire +#define smp_load_acquire(p) __smp_load_acquire(p) +#endif + +#else /* !CONFIG_SMP */ + +#ifndef smp_store_mb +#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); barrier(); } while (0) +#endif + +#ifndef smp_mb__before_atomic +#define smp_mb__before_atomic() barrier() +#endif + +#ifndef smp_mb__after_atomic +#define smp_mb__after_atomic() barrier() +#endif + +#ifndef smp_store_release +#define smp_store_release(p, v) \ +do { \ + compiletime_assert_atomic_type(*p); \ + barrier(); \ + WRITE_ONCE(*p, v); \ +} while (0) +#endif + +#ifndef smp_load_acquire +#define smp_load_acquire(p) \ +({ \ + __unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p); \ + compiletime_assert_atomic_type(*p); \ + barrier(); \ + (typeof(*p))___p1; \ +}) +#endif + +#endif /* CONFIG_SMP */ + +/* Barriers for virtual machine guests when talking to an SMP host */ +#define virt_mb() __smp_mb() +#define virt_rmb() __smp_rmb() +#define virt_wmb() __smp_wmb() +#define virt_store_mb(var, value) __smp_store_mb(var, value) +#define virt_mb__before_atomic() __smp_mb__before_atomic() +#define virt_mb__after_atomic() __smp_mb__after_atomic() +#define virt_store_release(p, v) __smp_store_release(p, v) +#define virt_load_acquire(p) __smp_load_acquire(p) + +/** + * smp_acquire__after_ctrl_dep() - Provide ACQUIRE ordering after a control dependency + * + * A control dependency provides a LOAD->STORE order, the additional RMB + * provides LOAD->LOAD order, together they provide LOAD->{LOAD,STORE} order, + * aka. (load)-ACQUIRE. + * + * Architectures that do not do load speculation can have this be barrier(). + */ +#ifndef smp_acquire__after_ctrl_dep +#define smp_acquire__after_ctrl_dep() smp_rmb() +#endif + +/** + * smp_cond_load_relaxed() - (Spin) wait for cond with no ordering guarantees + * @ptr: pointer to the variable to wait on + * @cond: boolean expression to wait for + * + * Equivalent to using READ_ONCE() on the condition variable. + * + * Due to C lacking lambda expressions we load the value of *ptr into a + * pre-named variable @VAL to be used in @cond. + */ +#ifndef smp_cond_load_relaxed +#define smp_cond_load_relaxed(ptr, cond_expr) ({ \ + typeof(ptr) __PTR = (ptr); \ + __unqual_scalar_typeof(*ptr) VAL; \ + for (;;) { \ + VAL = READ_ONCE(*__PTR); \ + if (cond_expr) \ + break; \ + cpu_relax(); \ + } \ + (typeof(*ptr))VAL; \ +}) +#endif + +/** + * smp_cond_load_acquire() - (Spin) wait for cond with ACQUIRE ordering + * @ptr: pointer to the variable to wait on + * @cond: boolean expression to wait for + * + * Equivalent to using smp_load_acquire() on the condition variable but employs + * the control dependency of the wait to reduce the barrier on many platforms. + */ +#ifndef smp_cond_load_acquire +#define smp_cond_load_acquire(ptr, cond_expr) ({ \ + __unqual_scalar_typeof(*ptr) _val; \ + _val = smp_cond_load_relaxed(ptr, cond_expr); \ + smp_acquire__after_ctrl_dep(); \ + (typeof(*ptr))_val; \ +}) +#endif + +/* + * pmem_wmb() ensures that all stores for which the modification + * are written to persistent storage by preceding instructions have + * updated persistent storage before any data access or data transfer + * caused by subsequent instructions is initiated. + */ +#ifndef pmem_wmb +#define pmem_wmb() wmb() +#endif + +#endif /* !__ASSEMBLY__ */ +#endif /* __ASM_GENERIC_BARRIER_H */ |