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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 "qemu/thread.h"
#include "qemu/queue.h"
#include "qemu/atomic.h"
#include "qemu/notify.h"
#include "qemu/sys_membarrier.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;
/*
* NotifierList used to force an RCU grace period. Accessed under
* rcu_registry_lock. Note that the notifier is called _outside_
* the thread!
*/
NotifierList force_rcu;
};
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 = qatomic_read(&rcu_gp_ctr);
qatomic_set(&p_rcu_reader->ctr, ctr);
/* Write p_rcu_reader->ctr before reading RCU-protected pointers. */
smp_mb_placeholder();
}
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;
}
/* Ensure that the critical section is seen to precede the
* store to p_rcu_reader->ctr. Together with the following
* smp_mb_placeholder(), this ensures writes to p_rcu_reader->ctr
* are sequentially consistent.
*/
qatomic_store_release(&p_rcu_reader->ctr, 0);
/* Write p_rcu_reader->ctr before reading p_rcu_reader->waiting. */
smp_mb_placeholder();
if (unlikely(qatomic_read(&p_rcu_reader->waiting))) {
qatomic_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);
/*
* Support for fork(). fork() support is enabled at startup.
*/
extern void rcu_enable_atfork(void);
extern void rcu_disable_atfork(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);
extern void drain_call_rcu(void);
/* 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);
typedef void RCUReadAuto;
static inline RCUReadAuto *rcu_read_auto_lock(void)
{
rcu_read_lock();
/* Anything non-NULL causes the cleanup function to be called */
return (void *)(uintptr_t)0x1;
}
static inline void rcu_read_auto_unlock(RCUReadAuto *r)
{
rcu_read_unlock();
}
G_DEFINE_AUTOPTR_CLEANUP_FUNC(RCUReadAuto, rcu_read_auto_unlock)
#define WITH_RCU_READ_LOCK_GUARD() \
WITH_RCU_READ_LOCK_GUARD_(glue(_rcu_read_auto, __COUNTER__))
#define WITH_RCU_READ_LOCK_GUARD_(var) \
for (g_autoptr(RCUReadAuto) var = rcu_read_auto_lock(); \
(var); rcu_read_auto_unlock(var), (var) = NULL)
#define RCU_READ_LOCK_GUARD() \
g_autoptr(RCUReadAuto) _rcu_read_auto __attribute__((unused)) = rcu_read_auto_lock()
/*
* Force-RCU notifiers tell readers that they should exit their
* read-side critical section.
*/
void rcu_add_force_rcu_notifier(Notifier *n);
void rcu_remove_force_rcu_notifier(Notifier *n);
#ifdef __cplusplus
}
#endif
#endif /* QEMU_RCU_H */
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