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#ifndef QEMU_RCU_H
#define QEMU_RCU_H
/*
* urcu-mb.h
*
* Userspace RCU header with explicit memory barrier.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* IBM's contributions to this file may be relicensed under LGPLv2 or later.
*/
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <unistd.h>
#include <stdint.h>
#include <stdbool.h>
#include <glib.h>
#include "qemu/compiler.h"
#include "qemu/thread.h"
#include "qemu/queue.h"
#include "qemu/atomic.h"
#ifdef __cplusplus
extern "C" {
#endif
/*
* Important !
*
* Each thread containing read-side critical sections must be registered
* with rcu_register_thread() before calling rcu_read_lock().
* rcu_unregister_thread() should be called before the thread exits.
*/
#ifdef DEBUG_RCU
#define rcu_assert(args...) assert(args)
#else
#define rcu_assert(args...)
#endif
/*
* Global quiescent period counter with low-order bits unused.
* Using a int rather than a char to eliminate false register dependencies
* causing stalls on some architectures.
*/
extern unsigned long rcu_gp_ctr;
extern QemuEvent rcu_gp_event;
struct rcu_reader_data {
/* Data used by both reader and synchronize_rcu() */
unsigned long ctr;
bool waiting;
/* Data used by reader only */
unsigned depth;
/* Data used for registry, protected by rcu_registry_lock */
QLIST_ENTRY(rcu_reader_data) node;
};
extern __thread struct rcu_reader_data rcu_reader;
static inline void rcu_read_lock(void)
{
struct rcu_reader_data *p_rcu_reader = &rcu_reader;
unsigned ctr;
if (p_rcu_reader->depth++ > 0) {
return;
}
ctr = atomic_read(&rcu_gp_ctr);
atomic_xchg(&p_rcu_reader->ctr, ctr);
if (atomic_read(&p_rcu_reader->waiting)) {
atomic_set(&p_rcu_reader->waiting, false);
qemu_event_set(&rcu_gp_event);
}
}
static inline void rcu_read_unlock(void)
{
struct rcu_reader_data *p_rcu_reader = &rcu_reader;
assert(p_rcu_reader->depth != 0);
if (--p_rcu_reader->depth > 0) {
return;
}
atomic_xchg(&p_rcu_reader->ctr, 0);
if (atomic_read(&p_rcu_reader->waiting)) {
atomic_set(&p_rcu_reader->waiting, false);
qemu_event_set(&rcu_gp_event);
}
}
extern void synchronize_rcu(void);
/*
* Reader thread registration.
*/
extern void rcu_register_thread(void);
extern void rcu_unregister_thread(void);
extern void rcu_after_fork(void);
struct rcu_head;
typedef void RCUCBFunc(struct rcu_head *head);
struct rcu_head {
struct rcu_head *next;
RCUCBFunc *func;
};
extern void call_rcu1(struct rcu_head *head, RCUCBFunc *func);
/* The operands of the minus operator must have the same type,
* which must be the one that we specify in the cast.
*/
#define call_rcu(head, func, field) \
call_rcu1(({ \
char __attribute__((unused)) \
offset_must_be_zero[-offsetof(__typeof__(*(head)), field)], \
func_type_invalid = (func) - (void (*)(__typeof__(head)))(func); \
&(head)->field; \
}), \
(RCUCBFunc *)(func))
#define g_free_rcu(obj, field) \
call_rcu1(({ \
char __attribute__((unused)) \
offset_must_be_zero[-offsetof(__typeof__(*(obj)), field)]; \
&(obj)->field; \
}), \
(RCUCBFunc *)g_free);
#ifdef __cplusplus
}
#endif
#endif /* QEMU_RCU_H */
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