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549887271a
Passing volatile-qualified pointers to the asm-generic implementations of the load-acquire macros results in a re-load from the stack due to the temporary result variable inheriting the volatile semantics thanks to the use of 'typeof()'. Define these temporary variables using 'unqual_scalar_typeof' to drop the volatile qualifier in the case that they are scalar types. Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Will Deacon <will@kernel.org>
262 lines
5.9 KiB
C
262 lines
5.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* Generic barrier definitions.
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*
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* It should be possible to use these on really simple architectures,
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* but it serves more as a starting point for new ports.
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*
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#ifndef __ASM_GENERIC_BARRIER_H
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#define __ASM_GENERIC_BARRIER_H
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#ifndef __ASSEMBLY__
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#include <linux/compiler.h>
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#ifndef nop
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#define nop() asm volatile ("nop")
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#endif
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/*
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* Force strict CPU ordering. And yes, this is required on UP too when we're
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* talking to devices.
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*
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* Fall back to compiler barriers if nothing better is provided.
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*/
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#ifndef mb
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#define mb() barrier()
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#endif
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#ifndef rmb
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#define rmb() mb()
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#endif
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#ifndef wmb
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#define wmb() mb()
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#endif
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#ifndef dma_rmb
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#define dma_rmb() rmb()
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#endif
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#ifndef dma_wmb
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#define dma_wmb() wmb()
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#endif
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#ifndef read_barrier_depends
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#define read_barrier_depends() do { } while (0)
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#endif
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#ifndef __smp_mb
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#define __smp_mb() mb()
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#endif
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#ifndef __smp_rmb
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#define __smp_rmb() rmb()
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#endif
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#ifndef __smp_wmb
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#define __smp_wmb() wmb()
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#endif
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#ifndef __smp_read_barrier_depends
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#define __smp_read_barrier_depends() read_barrier_depends()
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#endif
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#ifdef CONFIG_SMP
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#ifndef smp_mb
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#define smp_mb() __smp_mb()
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#endif
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#ifndef smp_rmb
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#define smp_rmb() __smp_rmb()
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#endif
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#ifndef smp_wmb
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#define smp_wmb() __smp_wmb()
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#endif
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#ifndef smp_read_barrier_depends
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#define smp_read_barrier_depends() __smp_read_barrier_depends()
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#endif
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#else /* !CONFIG_SMP */
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#ifndef smp_mb
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#define smp_mb() barrier()
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#endif
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#ifndef smp_rmb
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#define smp_rmb() barrier()
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#endif
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#ifndef smp_wmb
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#define smp_wmb() barrier()
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#endif
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#ifndef smp_read_barrier_depends
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#define smp_read_barrier_depends() do { } while (0)
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#endif
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#endif /* CONFIG_SMP */
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#ifndef __smp_store_mb
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#define __smp_store_mb(var, value) do { WRITE_ONCE(var, value); __smp_mb(); } while (0)
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#endif
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#ifndef __smp_mb__before_atomic
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#define __smp_mb__before_atomic() __smp_mb()
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#endif
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#ifndef __smp_mb__after_atomic
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#define __smp_mb__after_atomic() __smp_mb()
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#endif
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#ifndef __smp_store_release
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#define __smp_store_release(p, v) \
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do { \
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compiletime_assert_atomic_type(*p); \
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__smp_mb(); \
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WRITE_ONCE(*p, v); \
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} while (0)
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#endif
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#ifndef __smp_load_acquire
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#define __smp_load_acquire(p) \
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({ \
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__unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p); \
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compiletime_assert_atomic_type(*p); \
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__smp_mb(); \
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(typeof(*p))___p1; \
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})
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#endif
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#ifdef CONFIG_SMP
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#ifndef smp_store_mb
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#define smp_store_mb(var, value) __smp_store_mb(var, value)
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#endif
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#ifndef smp_mb__before_atomic
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#define smp_mb__before_atomic() __smp_mb__before_atomic()
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#endif
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#ifndef smp_mb__after_atomic
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#define smp_mb__after_atomic() __smp_mb__after_atomic()
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#endif
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#ifndef smp_store_release
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#define smp_store_release(p, v) __smp_store_release(p, v)
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#endif
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#ifndef smp_load_acquire
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#define smp_load_acquire(p) __smp_load_acquire(p)
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#endif
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#else /* !CONFIG_SMP */
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#ifndef smp_store_mb
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#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); barrier(); } while (0)
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#endif
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#ifndef smp_mb__before_atomic
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#define smp_mb__before_atomic() barrier()
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#endif
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#ifndef smp_mb__after_atomic
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#define smp_mb__after_atomic() barrier()
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#endif
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#ifndef smp_store_release
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#define smp_store_release(p, v) \
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do { \
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compiletime_assert_atomic_type(*p); \
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barrier(); \
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WRITE_ONCE(*p, v); \
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} while (0)
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#endif
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#ifndef smp_load_acquire
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#define smp_load_acquire(p) \
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({ \
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__unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p); \
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compiletime_assert_atomic_type(*p); \
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barrier(); \
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(typeof(*p))___p1; \
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})
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#endif
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#endif /* CONFIG_SMP */
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/* Barriers for virtual machine guests when talking to an SMP host */
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#define virt_mb() __smp_mb()
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#define virt_rmb() __smp_rmb()
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#define virt_wmb() __smp_wmb()
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#define virt_read_barrier_depends() __smp_read_barrier_depends()
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#define virt_store_mb(var, value) __smp_store_mb(var, value)
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#define virt_mb__before_atomic() __smp_mb__before_atomic()
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#define virt_mb__after_atomic() __smp_mb__after_atomic()
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#define virt_store_release(p, v) __smp_store_release(p, v)
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#define virt_load_acquire(p) __smp_load_acquire(p)
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/**
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* smp_acquire__after_ctrl_dep() - Provide ACQUIRE ordering after a control dependency
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*
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* A control dependency provides a LOAD->STORE order, the additional RMB
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* provides LOAD->LOAD order, together they provide LOAD->{LOAD,STORE} order,
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* aka. (load)-ACQUIRE.
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*
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* Architectures that do not do load speculation can have this be barrier().
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*/
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#ifndef smp_acquire__after_ctrl_dep
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#define smp_acquire__after_ctrl_dep() smp_rmb()
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#endif
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/**
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* smp_cond_load_relaxed() - (Spin) wait for cond with no ordering guarantees
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* @ptr: pointer to the variable to wait on
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* @cond: boolean expression to wait for
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*
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* Equivalent to using READ_ONCE() on the condition variable.
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*
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* Due to C lacking lambda expressions we load the value of *ptr into a
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* pre-named variable @VAL to be used in @cond.
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*/
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#ifndef smp_cond_load_relaxed
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#define smp_cond_load_relaxed(ptr, cond_expr) ({ \
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typeof(ptr) __PTR = (ptr); \
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__unqual_scalar_typeof(*ptr) VAL; \
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for (;;) { \
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VAL = READ_ONCE(*__PTR); \
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if (cond_expr) \
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break; \
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cpu_relax(); \
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} \
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(typeof(*ptr))VAL; \
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})
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#endif
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/**
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* smp_cond_load_acquire() - (Spin) wait for cond with ACQUIRE ordering
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* @ptr: pointer to the variable to wait on
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* @cond: boolean expression to wait for
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*
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* Equivalent to using smp_load_acquire() on the condition variable but employs
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* the control dependency of the wait to reduce the barrier on many platforms.
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*/
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#ifndef smp_cond_load_acquire
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#define smp_cond_load_acquire(ptr, cond_expr) ({ \
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__unqual_scalar_typeof(*ptr) _val; \
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_val = smp_cond_load_relaxed(ptr, cond_expr); \
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smp_acquire__after_ctrl_dep(); \
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(typeof(*ptr))_val; \
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})
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#endif
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#endif /* !__ASSEMBLY__ */
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#endif /* __ASM_GENERIC_BARRIER_H */
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