tools/virtio/linux/compiler.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef LINUX_COMPILER_H
#define LINUX_COMPILER_H

#include "../../../include/linux/compiler_types.h"

#define WRITE_ONCE(var, val) \
	(*((volatile typeof(val) *)(&(var))) = (val))

#define READ_ONCE(var) (*((volatile typeof(var) *)(&(var))))

#define __aligned(x) __attribute((__aligned__(x)))

/**
 * data_race - mark an expression as containing intentional data races
 *
 * This data_race() macro is useful for situations in which data races
 * should be forgiven.  One example is diagnostic code that accesses
 * shared variables but is not a part of the core synchronization design.
 * For example, if accesses to a given variable are protected by a lock,
 * except for diagnostic code, then the accesses under the lock should
 * be plain C-language accesses and those in the diagnostic code should
 * use data_race().  This way, KCSAN will complain if buggy lockless
 * accesses to that variable are introduced, even if the buggy accesses
 * are protected by READ_ONCE() or WRITE_ONCE().
 *
 * This macro *does not* affect normal code generation, but is a hint
 * to tooling that data races here are to be ignored.  If the access must
 * be atomic *and* KCSAN should ignore the access, use both data_race()
 * and READ_ONCE(), for example, data_race(READ_ONCE(x)).
 */
#define data_race(expr)							\
({									\
	__auto_type __v = (expr);					\
	__v;								\
})

#endif