1 #ifndef _URCU_BP_STATIC_H
2 #define _URCU_BP_STATIC_H
7 * Userspace RCU header.
9 * TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU
10 * RELEASE. See urcu.h for linking dynamically with the userspace rcu 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.
36 #include <urcu/compiler.h>
37 #include <urcu/arch.h>
38 #include <urcu/system.h>
39 #include <urcu/uatomic.h>
40 #include <urcu/list.h>
41 #include <urcu/tls-compat.h>
44 * This code section can only be included in LGPL 2.1 compatible source code.
45 * See below for the function call wrappers which can be used in code meant to
46 * be only linked with the Userspace RCU library. This comes with a small
47 * performance degradation on the read-side due to the added function calls.
48 * This is required to permit relinking with newer versions of the library.
56 #define rcu_assert(args...) assert(args)
58 #define rcu_assert(args...)
62 RCU_READER_ACTIVE_CURRENT
,
63 RCU_READER_ACTIVE_OLD
,
73 #define RCU_YIELD_READ (1 << 0)
74 #define RCU_YIELD_WRITE (1 << 1)
77 * Updates without RCU_MB are much slower. Account this in
80 /* maximum sleep delay, in us */
83 extern unsigned int rcu_yield_active
;
84 extern DECLARE_URCU_TLS(unsigned int, rcu_rand_yield
);
86 static inline void rcu_debug_yield_read(void)
88 if (rcu_yield_active
& RCU_YIELD_READ
)
89 if (rand_r(&URCU_TLS(rcu_rand_yield
)) & 0x1)
90 usleep(rand_r(&URCU_TLS(rcu_rand_yield
)) % MAX_SLEEP
);
93 static inline void rcu_debug_yield_write(void)
95 if (rcu_yield_active
& RCU_YIELD_WRITE
)
96 if (rand_r(&URCU_TLS(rcu_rand_yield
)) & 0x1)
97 usleep(rand_r(&URCU_TLS(rcu_rand_yield
)) % MAX_SLEEP
);
100 static inline void rcu_debug_yield_init(void)
102 URCU_TLS(rcu_rand_yield
) = time(NULL
) ^ (unsigned long) pthread_self();
105 static inline void rcu_debug_yield_read(void)
109 static inline void rcu_debug_yield_write(void)
113 static inline void rcu_debug_yield_init(void)
120 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use a
121 * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
123 #define RCU_GP_COUNT (1UL << 0)
124 /* Use the amount of bits equal to half of the architecture long size */
125 #define RCU_GP_CTR_PHASE (1UL << (sizeof(long) << 2))
126 #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
129 * Used internally by _rcu_read_lock.
131 extern void rcu_bp_register(void);
134 * Global quiescent period counter with low-order bits unused.
135 * Using a int rather than a char to eliminate false register dependencies
136 * causing stalls on some architectures.
138 extern unsigned long rcu_gp_ctr
;
141 /* Data used by both reader and synchronize_rcu() */
143 /* Data used for registry */
144 struct cds_list_head node
__attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
146 int alloc
; /* registry entry allocated */
150 * Bulletproof version keeps a pointer to a registry not part of the TLS.
151 * Adds a pointer dereference on the read-side, but won't require to unregister
154 extern DECLARE_URCU_TLS(struct rcu_reader
*, rcu_reader
);
156 static inline enum rcu_state
rcu_reader_state(unsigned long *ctr
)
161 return RCU_READER_INACTIVE
;
163 * Make sure both tests below are done on the same version of *value
164 * to insure consistency.
166 v
= CMM_LOAD_SHARED(*ctr
);
167 if (!(v
& RCU_GP_CTR_NEST_MASK
))
168 return RCU_READER_INACTIVE
;
169 if (!((v
^ rcu_gp_ctr
) & RCU_GP_CTR_PHASE
))
170 return RCU_READER_ACTIVE_CURRENT
;
171 return RCU_READER_ACTIVE_OLD
;
175 * Helper for _rcu_read_lock(). The format of rcu_gp_ctr (as well as
176 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
177 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
178 * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
179 * _rcu_read_lock() happen before the subsequent read-side critical section.
181 static inline void _rcu_read_lock_update(unsigned long tmp
)
183 if (caa_likely(!(tmp
& RCU_GP_CTR_NEST_MASK
))) {
184 _CMM_STORE_SHARED(URCU_TLS(rcu_reader
)->ctr
, _CMM_LOAD_SHARED(rcu_gp_ctr
));
187 _CMM_STORE_SHARED(URCU_TLS(rcu_reader
)->ctr
, tmp
+ RCU_GP_COUNT
);
191 * Enter an RCU read-side critical section.
193 * The first cmm_barrier() call ensures that the compiler does not reorder
194 * the body of _rcu_read_lock() with a mutex.
196 * This function and its helper are both less than 10 lines long. The
197 * intent is that this function meets the 10-line criterion in LGPL,
198 * allowing this function to be invoked directly from non-LGPL code.
200 static inline void _rcu_read_lock(void)
204 if (caa_unlikely(!URCU_TLS(rcu_reader
)))
205 rcu_bp_register(); /* If not yet registered. */
206 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
207 tmp
= URCU_TLS(rcu_reader
)->ctr
;
208 _rcu_read_lock_update(tmp
);
212 * Exit an RCU read-side critical section. This function is less than
213 * 10 lines of code, and is intended to be usable by non-LGPL code, as
214 * called out in LGPL.
216 static inline void _rcu_read_unlock(void)
219 * Finish using rcu before decrementing the pointer.
222 _CMM_STORE_SHARED(URCU_TLS(rcu_reader
)->ctr
, URCU_TLS(rcu_reader
)->ctr
- RCU_GP_COUNT
);
223 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
230 #endif /* _URCU_BP_STATIC_H */