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);
135 * Global grace period counter.
136 * Contains the current RCU_GP_CTR_PHASE.
137 * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
138 * Written to only by writer with mutex taken.
139 * Read by both writer and readers.
142 } __attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
144 extern struct rcu_gp rcu_gp
;
147 /* Data used by both reader and synchronize_rcu() */
149 /* Data used for registry */
150 struct cds_list_head node
__attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
152 int alloc
; /* registry entry allocated */
156 * Bulletproof version keeps a pointer to a registry not part of the TLS.
157 * Adds a pointer dereference on the read-side, but won't require to unregister
160 extern DECLARE_URCU_TLS(struct rcu_reader
*, rcu_reader
);
162 static inline enum rcu_state
rcu_reader_state(unsigned long *ctr
)
167 return RCU_READER_INACTIVE
;
169 * Make sure both tests below are done on the same version of *value
170 * to insure consistency.
172 v
= CMM_LOAD_SHARED(*ctr
);
173 if (!(v
& RCU_GP_CTR_NEST_MASK
))
174 return RCU_READER_INACTIVE
;
175 if (!((v
^ rcu_gp
.ctr
) & RCU_GP_CTR_PHASE
))
176 return RCU_READER_ACTIVE_CURRENT
;
177 return RCU_READER_ACTIVE_OLD
;
181 * Helper for _rcu_read_lock(). The format of rcu_gp.ctr (as well as
182 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
183 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
184 * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
185 * _rcu_read_lock() happen before the subsequent read-side critical section.
187 static inline void _rcu_read_lock_update(unsigned long tmp
)
189 if (caa_likely(!(tmp
& RCU_GP_CTR_NEST_MASK
))) {
190 _CMM_STORE_SHARED(URCU_TLS(rcu_reader
)->ctr
, _CMM_LOAD_SHARED(rcu_gp
.ctr
));
193 _CMM_STORE_SHARED(URCU_TLS(rcu_reader
)->ctr
, tmp
+ RCU_GP_COUNT
);
197 * Enter an RCU read-side critical section.
199 * The first cmm_barrier() call ensures that the compiler does not reorder
200 * the body of _rcu_read_lock() with a mutex.
202 * This function and its helper are both less than 10 lines long. The
203 * intent is that this function meets the 10-line criterion in LGPL,
204 * allowing this function to be invoked directly from non-LGPL code.
206 static inline void _rcu_read_lock(void)
210 if (caa_unlikely(!URCU_TLS(rcu_reader
)))
211 rcu_bp_register(); /* If not yet registered. */
212 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
213 tmp
= URCU_TLS(rcu_reader
)->ctr
;
214 _rcu_read_lock_update(tmp
);
218 * Exit an RCU read-side critical section. This function is less than
219 * 10 lines of code, and is intended to be usable by non-LGPL code, as
220 * called out in LGPL.
222 static inline void _rcu_read_unlock(void)
225 * Finish using rcu before decrementing the pointer.
228 _CMM_STORE_SHARED(URCU_TLS(rcu_reader
)->ctr
, URCU_TLS(rcu_reader
)->ctr
- RCU_GP_COUNT
);
229 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
233 * Returns whether within a RCU read-side critical section.
235 * This function is less than 10 lines long. The intent is that this
236 * function meets the 10-line criterion for LGPL, allowing this function
237 * to be invoked directly from non-LGPL code.
239 static inline int _rcu_read_ongoing(void)
241 if (caa_unlikely(!URCU_TLS(rcu_reader
)))
242 rcu_bp_register(); /* If not yet registered. */
243 return URCU_TLS(rcu_reader
)->ctr
& RCU_GP_CTR_NEST_MASK
;
250 #endif /* _URCU_BP_STATIC_H */