1 #ifndef _URCU_QSBR_STATIC_H
2 #define _URCU_QSBR_STATIC_H
7 * Userspace RCU QSBR header.
9 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-qsbr.h for linking
10 * dynamically with the userspace rcu QSBR library.
12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
13 * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
15 * This library is free software; you can redistribute it and/or
16 * modify it under the terms of the GNU Lesser General Public
17 * License as published by the Free Software Foundation; either
18 * version 2.1 of the License, or (at your option) any later version.
20 * This library is distributed in the hope that it will be useful,
21 * but WITHOUT ANY WARRANTY; without even the implied warranty of
22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23 * Lesser General Public License for more details.
25 * You should have received a copy of the GNU Lesser General Public
26 * License along with this library; if not, write to the Free Software
27 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
29 * IBM's contributions to this file may be relicensed under LGPLv2 or later.
39 #include <urcu/compiler.h>
40 #include <urcu/arch.h>
41 #include <urcu/system.h>
42 #include <urcu/uatomic.h>
43 #include <urcu/list.h>
44 #include <urcu/futex.h>
51 * This code section can only be included in LGPL 2.1 compatible source code.
52 * See below for the function call wrappers which can be used in code meant to
53 * be only linked with the Userspace RCU library. This comes with a small
54 * performance degradation on the read-side due to the added function calls.
55 * This is required to permit relinking with newer versions of the library.
59 * If a reader is really non-cooperative and refuses to commit its
60 * rcu_reader.ctr count to memory (there is no barrier in the reader
61 * per-se), kick it after a few loops waiting for it.
63 #define KICK_READER_LOOPS 10000
66 * Active attempts to check for reader Q.S. before calling futex().
68 #define RCU_QS_ACTIVE_ATTEMPTS 100
71 #define rcu_assert(args...) assert(args)
73 #define rcu_assert(args...)
82 #define YIELD_READ (1 << 0)
83 #define YIELD_WRITE (1 << 1)
85 /* maximum sleep delay, in us */
88 extern unsigned int yield_active
;
89 extern unsigned int __thread rand_yield
;
91 static inline void debug_yield_read(void)
93 if (yield_active
& YIELD_READ
)
94 if (rand_r(&rand_yield
) & 0x1)
95 usleep(rand_r(&rand_yield
) % MAX_SLEEP
);
98 static inline void debug_yield_write(void)
100 if (yield_active
& YIELD_WRITE
)
101 if (rand_r(&rand_yield
) & 0x1)
102 usleep(rand_r(&rand_yield
) % MAX_SLEEP
);
105 static inline void debug_yield_init(void)
107 rand_yield
= time(NULL
) ^ pthread_self();
110 static inline void debug_yield_read(void)
114 static inline void debug_yield_write(void)
118 static inline void debug_yield_init(void)
124 #define RCU_GP_ONLINE (1UL << 0)
125 #define RCU_GP_CTR (1UL << 1)
128 * Global quiescent period counter with low-order bits unused.
129 * Using a int rather than a char to eliminate false register dependencies
130 * causing stalls on some architectures.
132 extern unsigned long rcu_gp_ctr
;
135 /* Data used by both reader and synchronize_rcu() */
137 /* Data used for registry */
138 struct cds_list_head node
__attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
142 extern struct rcu_reader __thread rcu_reader
;
147 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
149 static inline void wake_up_gp(void)
151 if (unlikely(uatomic_read(&gp_futex
) == -1)) {
152 uatomic_set(&gp_futex
, 0);
153 futex_noasync(&gp_futex
, FUTEX_WAKE
, 1,
158 static inline int rcu_gp_ongoing(unsigned long *ctr
)
162 v
= CMM_LOAD_SHARED(*ctr
);
163 return v
&& (v
!= rcu_gp_ctr
);
166 static inline void _rcu_read_lock(void)
168 rcu_assert(rcu_reader
.ctr
);
171 static inline void _rcu_read_unlock(void)
175 static inline void _rcu_quiescent_state(void)
178 _CMM_STORE_SHARED(rcu_reader
.ctr
, _CMM_LOAD_SHARED(rcu_gp_ctr
));
179 cmm_smp_mb(); /* write rcu_reader.ctr before read futex */
184 static inline void _rcu_thread_offline(void)
187 CMM_STORE_SHARED(rcu_reader
.ctr
, 0);
188 cmm_smp_mb(); /* write rcu_reader.ctr before read futex */
190 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
193 static inline void _rcu_thread_online(void)
195 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
196 _CMM_STORE_SHARED(rcu_reader
.ctr
, CMM_LOAD_SHARED(rcu_gp_ctr
));
204 #endif /* _URCU_QSBR_STATIC_H */