1 #ifndef _URCU_BP_STATIC_H
2 #define _URCU_BP_STATIC_H
7 * Userspace RCU header.
9 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking
10 * 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.
37 #include <urcu/compiler.h>
38 #include <urcu/arch.h>
39 #include <urcu/system.h>
40 #include <urcu/uatomic.h>
41 #include <urcu/list.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 * Active attempts to check for reader Q.S. before calling sleep().
58 #define RCU_QS_ACTIVE_ATTEMPTS 100
61 #define rcu_assert(args...) assert(args)
63 #define rcu_assert(args...)
72 #define YIELD_READ (1 << 0)
73 #define YIELD_WRITE (1 << 1)
76 * Updates without RCU_MB are much slower. Account this in
79 /* maximum sleep delay, in us */
82 extern unsigned int yield_active
;
83 extern unsigned int __thread rand_yield
;
85 static inline void debug_yield_read(void)
87 if (yield_active
& YIELD_READ
)
88 if (rand_r(&rand_yield
) & 0x1)
89 usleep(rand_r(&rand_yield
) % MAX_SLEEP
);
92 static inline void debug_yield_write(void)
94 if (yield_active
& YIELD_WRITE
)
95 if (rand_r(&rand_yield
) & 0x1)
96 usleep(rand_r(&rand_yield
) % MAX_SLEEP
);
99 static inline void debug_yield_init(void)
101 rand_yield
= time(NULL
) ^ pthread_self();
104 static inline void debug_yield_read(void)
108 static inline void debug_yield_write(void)
112 static inline void debug_yield_init(void)
119 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use a
120 * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
122 #define RCU_GP_COUNT (1UL << 0)
123 /* Use the amount of bits equal to half of the architecture long size */
124 #define RCU_GP_CTR_PHASE (1UL << (sizeof(long) << 2))
125 #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
128 * Used internally by _rcu_read_lock.
130 extern void rcu_bp_register(void);
133 * Global quiescent period counter with low-order bits unused.
134 * Using a int rather than a char to eliminate false register dependencies
135 * causing stalls on some architectures.
137 extern long rcu_gp_ctr
;
140 /* Data used by both reader and synchronize_rcu() */
142 /* Data used for registry */
143 struct cds_list_head node
__attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
145 int alloc
; /* registry entry allocated */
149 * Bulletproof version keeps a pointer to a registry not part of the TLS.
150 * Adds a pointer dereference on the read-side, but won't require to unregister
153 extern struct rcu_reader __thread
*rcu_reader
;
155 static inline int rcu_old_gp_ongoing(long *value
)
162 * Make sure both tests below are done on the same version of *value
163 * to insure consistency.
165 v
= CMM_LOAD_SHARED(*value
);
166 return (v
& RCU_GP_CTR_NEST_MASK
) &&
167 ((v
^ rcu_gp_ctr
) & RCU_GP_CTR_PHASE
);
170 static inline void _rcu_read_lock(void)
174 /* Check if registered */
175 if (unlikely(!rcu_reader
))
178 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
179 tmp
= rcu_reader
->ctr
;
182 * RCU_GP_COUNT | (~RCU_GP_CTR_PHASE or RCU_GP_CTR_PHASE)
184 if (likely(!(tmp
& RCU_GP_CTR_NEST_MASK
))) {
185 _CMM_STORE_SHARED(rcu_reader
->ctr
, _CMM_LOAD_SHARED(rcu_gp_ctr
));
187 * Set active readers count for outermost nesting level before
188 * accessing the pointer.
192 _CMM_STORE_SHARED(rcu_reader
->ctr
, tmp
+ RCU_GP_COUNT
);
196 static inline void _rcu_read_unlock(void)
199 * Finish using rcu before decrementing the pointer.
202 _CMM_STORE_SHARED(rcu_reader
->ctr
, rcu_reader
->ctr
- RCU_GP_COUNT
);
203 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
210 #endif /* _URCU_BP_STATIC_H */
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