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/config.h>
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>
42 #include <urcu/tls-compat.h>
43 #include <urcu/debug.h>
46 * This code section can only be included in LGPL 2.1 compatible source code.
47 * See below for the function call wrappers which can be used in code meant to
48 * be only linked with the Userspace RCU library. This comes with a small
49 * performance degradation on the read-side due to the added function calls.
50 * This is required to permit relinking with newer versions of the library.
58 URCU_BP_READER_ACTIVE_CURRENT
,
59 URCU_BP_READER_ACTIVE_OLD
,
60 URCU_BP_READER_INACTIVE
,
64 * The trick here is that URCU_BP_GP_CTR_PHASE must be a multiple of 8 so we can use a
65 * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
67 #define URCU_BP_GP_COUNT (1UL << 0)
68 /* Use the amount of bits equal to half of the architecture long size */
69 #define URCU_BP_GP_CTR_PHASE (1UL << (sizeof(long) << 2))
70 #define URCU_BP_GP_CTR_NEST_MASK (URCU_BP_GP_CTR_PHASE - 1)
73 * Used internally by _urcu_bp_read_lock.
75 extern void urcu_bp_register(void);
79 * Global grace period counter.
80 * Contains the current URCU_BP_GP_CTR_PHASE.
81 * Also has a URCU_BP_GP_COUNT of 1, to accelerate the reader fast path.
82 * Written to only by writer with mutex taken.
83 * Read by both writer and readers.
86 } __attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
88 extern struct urcu_bp_gp urcu_bp_gp
;
90 struct urcu_bp_reader
{
91 /* Data used by both reader and urcu_bp_synchronize_rcu() */
93 /* Data used for registry */
94 struct cds_list_head node
__attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
96 int alloc
; /* registry entry allocated */
100 * Bulletproof version keeps a pointer to a registry not part of the TLS.
101 * Adds a pointer dereference on the read-side, but won't require to unregister
104 extern DECLARE_URCU_TLS(struct urcu_bp_reader
*, urcu_bp_reader
);
106 #ifdef CONFIG_RCU_FORCE_SYS_MEMBARRIER
107 #define urcu_bp_has_sys_membarrier 1
109 extern int urcu_bp_has_sys_membarrier
;
112 static inline void urcu_bp_smp_mb_slave(void)
114 if (caa_likely(urcu_bp_has_sys_membarrier
))
120 static inline enum urcu_bp_state
urcu_bp_reader_state(unsigned long *ctr
)
125 return URCU_BP_READER_INACTIVE
;
127 * Make sure both tests below are done on the same version of *value
128 * to insure consistency.
130 v
= CMM_LOAD_SHARED(*ctr
);
131 if (!(v
& URCU_BP_GP_CTR_NEST_MASK
))
132 return URCU_BP_READER_INACTIVE
;
133 if (!((v
^ urcu_bp_gp
.ctr
) & URCU_BP_GP_CTR_PHASE
))
134 return URCU_BP_READER_ACTIVE_CURRENT
;
135 return URCU_BP_READER_ACTIVE_OLD
;
139 * Helper for _urcu_bp_read_lock(). The format of urcu_bp_gp.ctr (as well as
140 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
141 * _urcu_bp_read_lock() nesting, and a lower-order bit that contains either zero
142 * or URCU_BP_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
143 * _urcu_bp_read_lock() happen before the subsequent read-side critical section.
145 static inline void _urcu_bp_read_lock_update(unsigned long tmp
)
147 if (caa_likely(!(tmp
& URCU_BP_GP_CTR_NEST_MASK
))) {
148 _CMM_STORE_SHARED(URCU_TLS(urcu_bp_reader
)->ctr
, _CMM_LOAD_SHARED(urcu_bp_gp
.ctr
));
149 urcu_bp_smp_mb_slave();
151 _CMM_STORE_SHARED(URCU_TLS(urcu_bp_reader
)->ctr
, tmp
+ URCU_BP_GP_COUNT
);
155 * Enter an RCU read-side critical section.
157 * The first cmm_barrier() call ensures that the compiler does not reorder
158 * the body of _urcu_bp_read_lock() with a mutex.
160 * This function and its helper are both less than 10 lines long. The
161 * intent is that this function meets the 10-line criterion in LGPL,
162 * allowing this function to be invoked directly from non-LGPL code.
164 static inline void _urcu_bp_read_lock(void)
168 if (caa_unlikely(!URCU_TLS(urcu_bp_reader
)))
169 urcu_bp_register(); /* If not yet registered. */
170 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
171 tmp
= URCU_TLS(urcu_bp_reader
)->ctr
;
172 urcu_assert((tmp
& URCU_BP_GP_CTR_NEST_MASK
) != URCU_BP_GP_CTR_NEST_MASK
);
173 _urcu_bp_read_lock_update(tmp
);
177 * Exit an RCU read-side critical section. This function is less than
178 * 10 lines of code, and is intended to be usable by non-LGPL code, as
179 * called out in LGPL.
181 static inline void _urcu_bp_read_unlock(void)
185 tmp
= URCU_TLS(urcu_bp_reader
)->ctr
;
186 urcu_assert(tmp
& URCU_BP_GP_CTR_NEST_MASK
);
187 /* Finish using rcu before decrementing the pointer. */
188 urcu_bp_smp_mb_slave();
189 _CMM_STORE_SHARED(URCU_TLS(urcu_bp_reader
)->ctr
, tmp
- URCU_BP_GP_COUNT
);
190 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
194 * Returns whether within a RCU read-side critical section.
196 * This function is less than 10 lines long. The intent is that this
197 * function meets the 10-line criterion for LGPL, allowing this function
198 * to be invoked directly from non-LGPL code.
200 static inline int _urcu_bp_read_ongoing(void)
202 if (caa_unlikely(!URCU_TLS(urcu_bp_reader
)))
203 urcu_bp_register(); /* If not yet registered. */
204 return URCU_TLS(urcu_bp_reader
)->ctr
& URCU_BP_GP_CTR_NEST_MASK
;
211 #endif /* _URCU_BP_STATIC_H */