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7 * Userspace RCU header with explicit memory barrier.
9 * This library is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
14 * This library is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with this library; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 * IBM's contributions to this file may be relicensed under LGPLv2 or later.
27 #include "qemu/thread.h"
28 #include "qemu/queue.h"
29 #include "qemu/atomic.h"
30 #include "qemu/notify.h"
31 #include "qemu/sys_membarrier.h"
32 #include "qemu/coroutine-tls.h"
37 * Each thread containing read-side critical sections must be registered
38 * with rcu_register_thread() before calling rcu_read_lock().
39 * rcu_unregister_thread() should be called before the thread exits.
43 #define rcu_assert(args...) assert(args)
45 #define rcu_assert(args...)
49 * Global quiescent period counter with low-order bits unused.
50 * Using a int rather than a char to eliminate false register dependencies
51 * causing stalls on some architectures.
53 extern unsigned long rcu_gp_ctr
;
55 extern QemuEvent rcu_gp_event
;
57 struct rcu_reader_data
{
58 /* Data used by both reader and synchronize_rcu() */
62 /* Data used by reader only */
65 /* Data used for registry, protected by rcu_registry_lock */
66 QLIST_ENTRY(rcu_reader_data
) node
;
69 * NotifierList used to force an RCU grace period. Accessed under
70 * rcu_registry_lock. Note that the notifier is called _outside_
73 NotifierList force_rcu
;
76 QEMU_DECLARE_CO_TLS(struct rcu_reader_data
, rcu_reader
)
78 static inline void rcu_read_lock(void)
80 struct rcu_reader_data
*p_rcu_reader
= get_ptr_rcu_reader();
83 if (p_rcu_reader
->depth
++ > 0) {
87 ctr
= qatomic_read(&rcu_gp_ctr
);
88 qatomic_set(&p_rcu_reader
->ctr
, ctr
);
91 * Read rcu_gp_ptr and write p_rcu_reader->ctr before reading
92 * RCU-protected pointers.
97 static inline void rcu_read_unlock(void)
99 struct rcu_reader_data
*p_rcu_reader
= get_ptr_rcu_reader();
101 assert(p_rcu_reader
->depth
!= 0);
102 if (--p_rcu_reader
->depth
> 0) {
106 /* Ensure that the critical section is seen to precede the
107 * store to p_rcu_reader->ctr. Together with the following
108 * smp_mb_placeholder(), this ensures writes to p_rcu_reader->ctr
109 * are sequentially consistent.
111 qatomic_store_release(&p_rcu_reader
->ctr
, 0);
113 /* Write p_rcu_reader->ctr before reading p_rcu_reader->waiting. */
114 smp_mb_placeholder();
115 if (unlikely(qatomic_read(&p_rcu_reader
->waiting
))) {
116 qatomic_set(&p_rcu_reader
->waiting
, false);
117 qemu_event_set(&rcu_gp_event
);
121 void synchronize_rcu(void);
124 * Reader thread registration.
126 void rcu_register_thread(void);
127 void rcu_unregister_thread(void);
130 * Support for fork(). fork() support is enabled at startup.
132 void rcu_enable_atfork(void);
133 void rcu_disable_atfork(void);
136 typedef void RCUCBFunc(struct rcu_head
*head
);
139 struct rcu_head
*next
;
143 void call_rcu1(struct rcu_head
*head
, RCUCBFunc
*func
);
144 void drain_call_rcu(void);
146 /* The operands of the minus operator must have the same type,
147 * which must be the one that we specify in the cast.
149 #define call_rcu(head, func, field) \
151 char __attribute__((unused)) \
152 offset_must_be_zero[-offsetof(typeof(*(head)), field)], \
153 func_type_invalid = (func) - (void (*)(typeof(head)))(func); \
158 #define g_free_rcu(obj, field) \
160 char __attribute__((unused)) \
161 offset_must_be_zero[-offsetof(typeof(*(obj)), field)]; \
164 (RCUCBFunc *)g_free);
166 typedef void RCUReadAuto
;
167 static inline RCUReadAuto
*rcu_read_auto_lock(void)
170 /* Anything non-NULL causes the cleanup function to be called */
171 return (void *)(uintptr_t)0x1;
174 static inline void rcu_read_auto_unlock(RCUReadAuto
*r
)
179 G_DEFINE_AUTOPTR_CLEANUP_FUNC(RCUReadAuto
, rcu_read_auto_unlock
)
181 #define WITH_RCU_READ_LOCK_GUARD() \
182 WITH_RCU_READ_LOCK_GUARD_(glue(_rcu_read_auto, __COUNTER__))
184 #define WITH_RCU_READ_LOCK_GUARD_(var) \
185 for (g_autoptr(RCUReadAuto) var = rcu_read_auto_lock(); \
186 (var); rcu_read_auto_unlock(var), (var) = NULL)
188 #define RCU_READ_LOCK_GUARD() \
189 g_autoptr(RCUReadAuto) _rcu_read_auto __attribute__((unused)) = rcu_read_auto_lock()
192 * Force-RCU notifiers tell readers that they should exit their
193 * read-side critical section.
195 void rcu_add_force_rcu_notifier(Notifier
*n
);
196 void rcu_remove_force_rcu_notifier(Notifier
*n
);
198 #endif /* QEMU_RCU_H */