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1 // SPDX-FileCopyrightText: 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
2 // SPDX-FileCopyrightText: 2009 Paul E. McKenney, IBM Corporation.
4 // SPDX-License-Identifier: LGPL-2.1-or-later
6 #ifndef _URCU_SIGNAL_STATIC_H
7 #define _URCU_SIGNAL_STATIC_H
10 * Userspace RCU header.
12 * TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU
13 * RELEASE. See urcu.h for linking dynamically with the userspace rcu library.
15 * IBM's contributions to this file may be relicensed under LGPLv2 or later.
23 #include <urcu/debug.h>
24 #include <urcu/config.h>
25 #include <urcu/compiler.h>
26 #include <urcu/arch.h>
27 #include <urcu/system.h>
28 #include <urcu/uatomic.h>
29 #include <urcu/list.h>
30 #include <urcu/futex.h>
31 #include <urcu/tls-compat.h>
32 #include <urcu/static/urcu-common.h>
33 #include <urcu/static/urcu-signal-nr.h>
40 * This code section can only be included in LGPL 2.1 compatible source code.
41 * See below for the function call wrappers which can be used in code meant to
42 * be only linked with the Userspace RCU library. This comes with a small
43 * performance degradation on the read-side due to the added function calls.
44 * This is required to permit relinking with newer versions of the library.
47 extern struct urcu_gp urcu_signal_gp
;
49 extern DECLARE_URCU_TLS(struct urcu_reader
, urcu_signal_reader
);
52 * Helper for _rcu_read_lock(). The format of urcu_signal_gp.ctr (as well as
53 * the per-thread rcu_reader.ctr) has the lower-order bits containing a count of
54 * _rcu_read_lock() nesting, and a single high-order URCU_BP_GP_CTR_PHASE bit
55 * that contains either zero or one. The cmm_barrier() ensures that the accesses in
56 * _rcu_read_lock() happen before the subsequent read-side critical section.
58 static inline void _urcu_signal_read_lock_update(unsigned long tmp
)
60 if (caa_likely(!(tmp
& URCU_GP_CTR_NEST_MASK
))) {
61 _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader
).ctr
, _CMM_LOAD_SHARED(urcu_signal_gp
.ctr
));
64 _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader
).ctr
, tmp
+ URCU_GP_COUNT
);
68 * Enter an RCU read-side critical section.
70 * The first cmm_barrier() call ensures that the compiler does not reorder
71 * the body of _rcu_read_lock() with a mutex.
73 * This function and its helper are both less than 10 lines long. The
74 * intent is that this function meets the 10-line criterion in LGPL,
75 * allowing this function to be invoked directly from non-LGPL code.
77 static inline void _urcu_signal_read_lock(void)
81 urcu_assert_debug(URCU_TLS(urcu_signal_reader
).registered
);
83 tmp
= URCU_TLS(urcu_signal_reader
).ctr
;
84 urcu_assert_debug((tmp
& URCU_GP_CTR_NEST_MASK
) != URCU_GP_CTR_NEST_MASK
);
85 _urcu_signal_read_lock_update(tmp
);
89 * This is a helper function for _rcu_read_unlock().
91 * The first cmm_barrier() call ensures that the critical section is
92 * seen to precede the store to rcu_reader.ctr.
93 * The second cmm_barrier() call ensures that we write to rcu_reader.ctr
94 * before reading the update-side futex.
96 static inline void _urcu_signal_read_unlock_update_and_wakeup(unsigned long tmp
)
98 if (caa_likely((tmp
& URCU_GP_CTR_NEST_MASK
) == URCU_GP_COUNT
)) {
100 _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader
).ctr
, tmp
- URCU_GP_COUNT
);
102 urcu_common_wake_up_gp(&urcu_signal_gp
);
104 _CMM_STORE_SHARED(URCU_TLS(urcu_signal_reader
).ctr
, tmp
- URCU_GP_COUNT
);
108 * Exit an RCU read-side critical section. Both this function and its
109 * helper are smaller than 10 lines of code, and are intended to be
110 * usable by non-LGPL code, as called out in LGPL.
112 static inline void _urcu_signal_read_unlock(void)
116 urcu_assert_debug(URCU_TLS(urcu_signal_reader
).registered
);
117 tmp
= URCU_TLS(urcu_signal_reader
).ctr
;
118 urcu_assert_debug(tmp
& URCU_GP_CTR_NEST_MASK
);
119 _urcu_signal_read_unlock_update_and_wakeup(tmp
);
120 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
124 * Returns whether within a RCU read-side critical section.
126 * This function is less than 10 lines long. The intent is that this
127 * function meets the 10-line criterion for LGPL, allowing this function
128 * to be invoked directly from non-LGPL code.
130 static inline int _urcu_signal_read_ongoing(void)
132 return URCU_TLS(urcu_signal_reader
).ctr
& URCU_GP_CTR_NEST_MASK
;
139 #endif /* _URCU_SIGNAL_STATIC_H */
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