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@polymtl.ca>
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_arch.h>
43 #include <urcu/list.h>
45 #define futex(...) syscall(__NR_futex, __VA_ARGS__)
50 * This code section can only be included in LGPL 2.1 compatible source code.
51 * See below for the function call wrappers which can be used in code meant to
52 * be only linked with the Userspace RCU library. This comes with a small
53 * performance degradation on the read-side due to the added function calls.
54 * This is required to permit relinking with newer versions of the library.
58 * If a reader is really non-cooperative and refuses to commit its
59 * urcu_reader.ctr count to memory (there is no barrier in the reader
60 * per-se), kick it after a few loops waiting for it.
62 #define KICK_READER_LOOPS 10000
65 * Active attempts to check for reader Q.S. before calling futex().
67 #define RCU_QS_ACTIVE_ATTEMPTS 100
70 #define rcu_assert(args...) assert(args)
72 #define rcu_assert(args...)
81 #define YIELD_READ (1 << 0)
82 #define YIELD_WRITE (1 << 1)
84 /* maximum sleep delay, in us */
87 extern unsigned int yield_active
;
88 extern unsigned int __thread rand_yield
;
90 static inline void debug_yield_read(void)
92 if (yield_active
& YIELD_READ
)
93 if (rand_r(&rand_yield
) & 0x1)
94 usleep(rand_r(&rand_yield
) % MAX_SLEEP
);
97 static inline void debug_yield_write(void)
99 if (yield_active
& YIELD_WRITE
)
100 if (rand_r(&rand_yield
) & 0x1)
101 usleep(rand_r(&rand_yield
) % MAX_SLEEP
);
104 static inline void debug_yield_init(void)
106 rand_yield
= time(NULL
) ^ pthread_self();
109 static inline void debug_yield_read(void)
113 static inline void debug_yield_write(void)
117 static inline void debug_yield_init(void)
123 static inline void reader_barrier()
128 #define RCU_GP_ONLINE (1UL << 0)
129 #define RCU_GP_CTR (1UL << 1)
132 * Global quiescent period counter with low-order bits unused.
133 * Using a int rather than a char to eliminate false register dependencies
134 * causing stalls on some architectures.
136 extern unsigned long urcu_gp_ctr
;
139 /* Data used by both reader and synchronize_rcu() */
141 /* Data used for registry */
142 struct list_head head
__attribute__((aligned(CACHE_LINE_SIZE
)));
146 extern struct urcu_reader __thread urcu_reader
;
151 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
153 static inline void wake_up_gp(void)
155 if (unlikely(uatomic_read(&gp_futex
) == -1)) {
156 uatomic_set(&gp_futex
, 0);
157 futex(&gp_futex
, FUTEX_WAKE
, 1,
162 #if (BITS_PER_LONG < 64)
163 static inline int rcu_gp_ongoing(unsigned long *value
)
165 unsigned long reader_gp
;
169 reader_gp
= LOAD_SHARED(*value
);
170 return reader_gp
&& ((reader_gp
^ urcu_gp_ctr
) & RCU_GP_CTR
);
172 #else /* !(BITS_PER_LONG < 64) */
173 static inline int rcu_gp_ongoing(unsigned long *value
)
175 unsigned long reader_gp
;
179 reader_gp
= LOAD_SHARED(*value
);
180 return reader_gp
&& (reader_gp
- urcu_gp_ctr
> ULONG_MAX
/ 2);
182 #endif /* !(BITS_PER_LONG < 64) */
184 static inline void _rcu_read_lock(void)
186 rcu_assert(urcu_reader
.ctr
);
189 static inline void _rcu_read_unlock(void)
193 static inline void _rcu_quiescent_state(void)
196 _STORE_SHARED(urcu_reader
.ctr
, _LOAD_SHARED(urcu_gp_ctr
));
197 smp_mb(); /* write urcu_reader.ctr before read futex */
202 static inline void _rcu_thread_offline(void)
205 STORE_SHARED(urcu_reader
.ctr
, 0);
206 smp_mb(); /* write urcu_reader.ctr before read futex */
210 static inline void _rcu_thread_online(void)
212 _STORE_SHARED(urcu_reader
.ctr
, LOAD_SHARED(urcu_gp_ctr
));
216 #endif /* _URCU_QSBR_STATIC_H */