bcachefs-tools/include/linux/rcupdate.h

#ifndef __TOOLS_LINUX_RCUPDATE_H
#define __TOOLS_LINUX_RCUPDATE_H

#include <urcu.h>
#include <linux/compiler.h>
#include <linux/cleanup.h>

#define ULONG_CMP_GE(a, b)      (ULONG_MAX / 2 >= (a) - (b))

#define rcu_dereference_check(p, c)	rcu_dereference(p)
#define rcu_dereference_raw(p)		rcu_dereference(p)
#define rcu_dereference_protected(p, c)	rcu_dereference(p)
#define rcu_access_pointer(p)		READ_ONCE(p)

#define kfree_rcu(ptr, rcu_head)	kfree(ptr) /* XXX */
#define kfree_rcu_mightsleep(ptr)	kfree(ptr) /* XXX */
#define kvfree_rcu(ptr, rcu_head)	kfree(ptr) /* XXX */
#define kvfree_rcu_mightsleep(ptr)	kfree(ptr) /* XXX */

#define RCU_INIT_POINTER(p, v)		WRITE_ONCE(p, v)

/* Has the specified rcu_head structure been handed to call_rcu()? */

/**
 * rcu_head_init - Initialize rcu_head for rcu_head_after_call_rcu()
 * @rhp: The rcu_head structure to initialize.
 *
 * If you intend to invoke rcu_head_after_call_rcu() to test whether a
 * given rcu_head structure has already been passed to call_rcu(), then
 * you must also invoke this rcu_head_init() function on it just after
 * allocating that structure.  Calls to this function must not race with
 * calls to call_rcu(), rcu_head_after_call_rcu(), or callback invocation.
 */
static inline void rcu_head_init(struct rcu_head *rhp)
{
	rhp->func = (void *)~0L;
}

static inline bool
rcu_head_after_call_rcu(struct rcu_head *rhp,
			void (*f)(struct rcu_head *head))
{
	void (*func)(struct rcu_head *head) = READ_ONCE(rhp->func);

	if (func == f)
		return true;
	return false;
}

DEFINE_LOCK_GUARD_0(rcu,
	do {
		rcu_read_lock();
		/*
		 * sparse doesn't call the cleanup function,
		 * so just release immediately and don't track
		 * the context. We don't need to anyway, since
		 * the whole point of the guard is to not need
		 * the explicit unlock.
		 */
		__release(RCU);
	} while (0),
	rcu_read_unlock())

#endif /* __TOOLS_LINUX_RCUPDATE_H */