1 #ifndef QEMU_RCU_H 2 #define QEMU_RCU_H 3 4 /* 5 * urcu-mb.h 6 * 7 * Userspace RCU header with explicit memory barrier. 8 * 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. 13 * 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. 18 * 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 22 * 23 * IBM's contributions to this file may be relicensed under LGPLv2 or later. 24 */ 25 26 #include <glib.h> 27 28 #include "qemu/thread.h" 29 #include "qemu/queue.h" 30 #include "qemu/atomic.h" 31 32 #ifdef __cplusplus 33 extern "C" { 34 #endif 35 36 /* 37 * Important ! 38 * 39 * Each thread containing read-side critical sections must be registered 40 * with rcu_register_thread() before calling rcu_read_lock(). 41 * rcu_unregister_thread() should be called before the thread exits. 42 */ 43 44 #ifdef DEBUG_RCU 45 #define rcu_assert(args...) assert(args) 46 #else 47 #define rcu_assert(args...) 48 #endif 49 50 /* 51 * Global quiescent period counter with low-order bits unused. 52 * Using a int rather than a char to eliminate false register dependencies 53 * causing stalls on some architectures. 54 */ 55 extern unsigned long rcu_gp_ctr; 56 57 extern QemuEvent rcu_gp_event; 58 59 struct rcu_reader_data { 60 /* Data used by both reader and synchronize_rcu() */ 61 unsigned long ctr; 62 bool waiting; 63 64 /* Data used by reader only */ 65 unsigned depth; 66 67 /* Data used for registry, protected by rcu_registry_lock */ 68 QLIST_ENTRY(rcu_reader_data) node; 69 }; 70 71 extern __thread struct rcu_reader_data rcu_reader; 72 73 static inline void rcu_read_lock(void) 74 { 75 struct rcu_reader_data *p_rcu_reader = &rcu_reader; 76 unsigned ctr; 77 78 if (p_rcu_reader->depth++ > 0) { 79 return; 80 } 81 82 ctr = atomic_read(&rcu_gp_ctr); 83 atomic_xchg(&p_rcu_reader->ctr, ctr); 84 } 85 86 static inline void rcu_read_unlock(void) 87 { 88 struct rcu_reader_data *p_rcu_reader = &rcu_reader; 89 90 assert(p_rcu_reader->depth != 0); 91 if (--p_rcu_reader->depth > 0) { 92 return; 93 } 94 95 atomic_xchg(&p_rcu_reader->ctr, 0); 96 if (unlikely(atomic_read(&p_rcu_reader->waiting))) { 97 atomic_set(&p_rcu_reader->waiting, false); 98 qemu_event_set(&rcu_gp_event); 99 } 100 } 101 102 extern void synchronize_rcu(void); 103 104 /* 105 * Reader thread registration. 106 */ 107 extern void rcu_register_thread(void); 108 extern void rcu_unregister_thread(void); 109 extern void rcu_after_fork(void); 110 111 struct rcu_head; 112 typedef void RCUCBFunc(struct rcu_head *head); 113 114 struct rcu_head { 115 struct rcu_head *next; 116 RCUCBFunc *func; 117 }; 118 119 extern void call_rcu1(struct rcu_head *head, RCUCBFunc *func); 120 121 /* The operands of the minus operator must have the same type, 122 * which must be the one that we specify in the cast. 123 */ 124 #define call_rcu(head, func, field) \ 125 call_rcu1(({ \ 126 char __attribute__((unused)) \ 127 offset_must_be_zero[-offsetof(typeof(*(head)), field)], \ 128 func_type_invalid = (func) - (void (*)(typeof(head)))(func); \ 129 &(head)->field; \ 130 }), \ 131 (RCUCBFunc *)(func)) 132 133 #define g_free_rcu(obj, field) \ 134 call_rcu1(({ \ 135 char __attribute__((unused)) \ 136 offset_must_be_zero[-offsetof(typeof(*(obj)), field)]; \ 137 &(obj)->field; \ 138 }), \ 139 (RCUCBFunc *)g_free); 140 141 #ifdef __cplusplus 142 } 143 #endif 144 145 #endif /* QEMU_RCU_H */ 146