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1 /* Copyright (C) 2003-2014 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library. If not, see
16 <http://www.gnu.org/licenses/>. */
18 #ifndef _LOWLEVELLOCK_H
19 #define _LOWLEVELLOCK_H 1
22 #include <sys/param.h>
23 #include <bits/pthreadtypes.h>
26 #include <kernel-features.h>
30 #define FUTEX_REQUEUE 3
31 #define FUTEX_CMP_REQUEUE 4
32 #define FUTEX_WAKE_OP 5
33 #define FUTEX_OP_CLEAR_WAKE_IF_GT_ONE ((4 << 24) | 1)
34 #define FUTEX_LOCK_PI 6
35 #define FUTEX_UNLOCK_PI 7
36 #define FUTEX_TRYLOCK_PI 8
37 #define FUTEX_WAIT_BITSET 9
38 #define FUTEX_WAKE_BITSET 10
39 #define FUTEX_WAIT_REQUEUE_PI 11
40 #define FUTEX_CMP_REQUEUE_PI 12
41 #define FUTEX_PRIVATE_FLAG 128
42 #define FUTEX_CLOCK_REALTIME 256
44 #define FUTEX_BITSET_MATCH_ANY 0xffffffff
46 /* Values for 'private' parameter of locking macros. Yes, the
47 definition seems to be backwards. But it is not. The bit will be
48 reversed before passing to the system call. */
50 #define LLL_SHARED FUTEX_PRIVATE_FLAG
53 #if !defined NOT_IN_libc || defined IS_IN_rtld
54 /* In libc.so or ld.so all futexes are private. */
55 # ifdef __ASSUME_PRIVATE_FUTEX
56 # define __lll_private_flag(fl, private) \
57 ((fl) | FUTEX_PRIVATE_FLAG)
59 # define __lll_private_flag(fl, private) \
60 ((fl) | THREAD_GETMEM (THREAD_SELF, header.private_futex))
63 # ifdef __ASSUME_PRIVATE_FUTEX
64 # define __lll_private_flag(fl, private) \
65 (((fl) | FUTEX_PRIVATE_FLAG) ^ (private))
67 # define __lll_private_flag(fl, private) \
68 (__builtin_constant_p (private) \
70 ? ((fl) | THREAD_GETMEM (THREAD_SELF, header.private_futex)) \
72 : ((fl) | (((private) ^ FUTEX_PRIVATE_FLAG) \
73 & THREAD_GETMEM (THREAD_SELF, header.private_futex))))
78 #define lll_futex_wait(futexp, val, private) \
79 lll_futex_timed_wait(futexp, val, NULL, private)
81 #define lll_futex_timed_wait(futexp, val, timespec, private) \
83 INTERNAL_SYSCALL_DECL (__err); \
85 __ret = INTERNAL_SYSCALL (futex, __err, 4, (long) (futexp), \
86 __lll_private_flag (FUTEX_WAIT, private), \
88 INTERNAL_SYSCALL_ERROR_P (__ret, __err) ? -__ret : __ret; \
91 #define lll_futex_timed_wait_bitset(futexp, val, timespec, clockbit, private) \
93 INTERNAL_SYSCALL_DECL (__err); \
95 int __op = FUTEX_WAIT_BITSET | clockbit; \
96 __ret = INTERNAL_SYSCALL (futex, __err, 6, (long) (futexp), \
97 __lll_private_flag (__op, private), \
98 (val), (timespec), NULL /* Unused. */, \
99 FUTEX_BITSET_MATCH_ANY); \
100 INTERNAL_SYSCALL_ERROR_P (__ret, __err) ? -__ret : __ret; \
103 #define lll_futex_wake(futexp, nr, private) \
105 INTERNAL_SYSCALL_DECL (__err); \
107 __ret = INTERNAL_SYSCALL (futex, __err, 4, (long) (futexp), \
108 __lll_private_flag (FUTEX_WAKE, private), \
110 INTERNAL_SYSCALL_ERROR_P (__ret, __err) ? -__ret : __ret; \
113 #define lll_robust_dead(futexv, private) \
116 int *__futexp = &(futexv); \
117 atomic_or (__futexp, FUTEX_OWNER_DIED); \
118 lll_futex_wake (__futexp, 1, private); \
122 /* Returns non-zero if error happened, zero if success. */
123 #define lll_futex_requeue(futexp, nr_wake, nr_move, mutex, val, private) \
125 INTERNAL_SYSCALL_DECL (__err); \
127 __ret = INTERNAL_SYSCALL (futex, __err, 6, (long) (futexp), \
128 __lll_private_flag (FUTEX_CMP_REQUEUE, private),\
129 (nr_wake), (nr_move), (mutex), (val)); \
130 INTERNAL_SYSCALL_ERROR_P (__ret, __err); \
133 /* Returns non-zero if error happened, zero if success. */
134 #define lll_futex_wake_unlock(futexp, nr_wake, nr_wake2, futexp2, private) \
136 INTERNAL_SYSCALL_DECL (__err); \
139 __ret = INTERNAL_SYSCALL (futex, __err, 6, (futexp), \
140 __lll_private_flag (FUTEX_WAKE_OP, private), \
141 (nr_wake), (nr_wake2), (futexp2), \
142 FUTEX_OP_CLEAR_WAKE_IF_GT_ONE); \
143 INTERNAL_SYSCALL_ERROR_P (__ret, __err); \
146 /* Priority Inheritance support. */
147 #define lll_futex_wait_requeue_pi(futexp, val, mutex, private) \
148 lll_futex_timed_wait_requeue_pi (futexp, val, NULL, 0, mutex, private)
150 #define lll_futex_timed_wait_requeue_pi(futexp, val, timespec, clockbit, \
153 INTERNAL_SYSCALL_DECL (__err); \
155 int __op = FUTEX_WAIT_REQUEUE_PI | clockbit; \
157 __ret = INTERNAL_SYSCALL (futex, __err, 5, (futexp), \
158 __lll_private_flag (__op, private), \
159 (val), (timespec), mutex); \
160 INTERNAL_SYSCALL_ERROR_P (__ret, __err) ? -__ret : __ret; \
163 #define lll_futex_cmp_requeue_pi(futexp, nr_wake, nr_move, mutex, val, priv) \
165 INTERNAL_SYSCALL_DECL (__err); \
168 __ret = INTERNAL_SYSCALL (futex, __err, 6, (futexp), \
169 __lll_private_flag (FUTEX_CMP_REQUEUE_PI, priv),\
170 (nr_wake), (nr_move), (mutex), (val)); \
171 INTERNAL_SYSCALL_ERROR_P (__ret, __err); \
174 static inline int __attribute__((always_inline
))
175 __lll_trylock(int *futex
)
177 return atomic_compare_and_exchange_val_acq (futex
, 1, 0) != 0;
179 #define lll_trylock(lock) __lll_trylock (&(lock))
182 static inline int __attribute__((always_inline
))
183 __lll_cond_trylock(int *futex
)
185 return atomic_compare_and_exchange_val_acq (futex
, 2, 0) != 0;
187 #define lll_cond_trylock(lock) __lll_cond_trylock (&(lock))
190 static inline int __attribute__((always_inline
))
191 __lll_robust_trylock(int *futex
, int id
)
193 return atomic_compare_and_exchange_val_acq (futex
, id
, 0) != 0;
195 #define lll_robust_trylock(lock, id) \
196 __lll_robust_trylock (&(lock), id)
198 extern void __lll_lock_wait_private (int *futex
) attribute_hidden
;
199 extern void __lll_lock_wait (int *futex
, int private) attribute_hidden
;
200 extern int __lll_robust_lock_wait (int *futex
, int private) attribute_hidden
;
202 #define __lll_lock(futex, private) \
204 int *__futex = (futex); \
205 if (__builtin_expect (atomic_compare_and_exchange_bool_acq (__futex, \
208 if (__builtin_constant_p (private) && (private) == LLL_PRIVATE) \
209 __lll_lock_wait_private (__futex); \
211 __lll_lock_wait (__futex, private); \
214 #define lll_lock(futex, private) __lll_lock (&(futex), private)
217 #define __lll_robust_lock(futex, id, private) \
219 int *__futex = (futex); \
222 if (__builtin_expect (atomic_compare_and_exchange_bool_acq (__futex, id, \
224 __val = __lll_robust_lock_wait (__futex, private); \
227 #define lll_robust_lock(futex, id, private) \
228 __lll_robust_lock (&(futex), id, private)
231 static inline void __attribute__ ((always_inline
))
232 __lll_cond_lock (int *futex
, int private)
234 if (atomic_compare_and_exchange_bool_acq (futex
, 2, 0) != 0)
235 __lll_lock_wait (futex
, private);
237 #define lll_cond_lock(futex, private) __lll_cond_lock (&(futex), private)
240 #define lll_robust_cond_lock(futex, id, private) \
241 __lll_robust_lock (&(futex), (id) | FUTEX_WAITERS, private)
244 extern int __lll_timedlock_wait (int *futex
, const struct timespec
*,
245 int private) attribute_hidden
;
246 extern int __lll_robust_timedlock_wait (int *futex
, const struct timespec
*,
247 int private) attribute_hidden
;
249 static inline int __attribute__ ((always_inline
))
250 __lll_timedlock (int *futex
, const struct timespec
*abstime
, int private)
253 if (atomic_compare_and_exchange_bool_acq (futex
, 1, 0) != 0)
254 result
= __lll_timedlock_wait (futex
, abstime
, private);
257 #define lll_timedlock(futex, abstime, private) \
258 __lll_timedlock (&(futex), abstime, private)
261 static inline int __attribute__ ((always_inline
))
262 __lll_robust_timedlock (int *futex
, const struct timespec
*abstime
,
266 if (atomic_compare_and_exchange_bool_acq (futex
, id
, 0) != 0)
267 result
= __lll_robust_timedlock_wait (futex
, abstime
, private);
270 #define lll_robust_timedlock(futex, abstime, id, private) \
271 __lll_robust_timedlock (&(futex), abstime, id, private)
274 #define __lll_unlock(futex, private) \
276 int *__futex = (futex); \
277 int __val = atomic_exchange_rel (__futex, 0); \
279 if (__builtin_expect (__val > 1, 0)) \
280 lll_futex_wake (__futex, 1, private); \
282 #define lll_unlock(futex, private) __lll_unlock(&(futex), private)
285 #define __lll_robust_unlock(futex, private) \
287 int *__futex = (futex); \
288 int __val = atomic_exchange_rel (__futex, 0); \
290 if (__builtin_expect (__val & FUTEX_WAITERS, 0)) \
291 lll_futex_wake (__futex, 1, private); \
293 #define lll_robust_unlock(futex, private) \
294 __lll_robust_unlock(&(futex), private)
297 #define lll_islocked(futex) \
301 /* Our internal lock implementation is identical to the binary-compatible
302 mutex implementation. */
304 /* Initializers for lock. */
305 #define LLL_LOCK_INITIALIZER (0)
306 #define LLL_LOCK_INITIALIZER_LOCKED (1)
308 /* The states of a lock are:
310 1 - taken by one user
311 >1 - taken by more users */
313 /* The kernel notifies a process which uses CLONE_CHILD_CLEARTID via futex
314 wakeup when the clone terminates. The memory location contains the
315 thread ID while the clone is running and is reset to zero
317 #define lll_wait_tid(tid) \
319 __typeof (tid) __tid; \
320 while ((__tid = (tid)) != 0) \
321 lll_futex_wait (&(tid), __tid, LLL_SHARED); \
324 extern int __lll_timedwait_tid (int *, const struct timespec
*)
327 #define lll_timedwait_tid(tid, abstime) \
331 __res = __lll_timedwait_tid (&(tid), (abstime)); \
335 /* Implement __libc_lock_lock using exchange_and_add, which expands into
336 a single instruction on XLP processors. We enable this for all MIPS
337 processors as atomic_exchange_and_add_acq and
338 atomic_compare_and_exchange_acq take the same time to execute.
339 This is a simplified expansion of ({ lll_lock (NAME, LLL_PRIVATE); 0; }).
341 Note: __lll_lock_wait_private() resets lock value to '2', which prevents
342 unbounded increase of the lock value and [with billions of threads]
344 #define __libc_lock_lock(NAME) \
346 int *__futex = &(NAME); \
347 if (__builtin_expect (atomic_exchange_and_add_acq (__futex, 1), 0)) \
348 __lll_lock_wait_private (__futex); \
352 #ifdef _MIPS_ARCH_XLP
353 /* The generic version using a single atomic_compare_and_exchange_acq takes
354 less time for non-XLP processors, so we use below for XLP only. */
355 # define __libc_lock_trylock(NAME) \
357 int *__futex = &(NAME); \
358 int __result = atomic_exchange_and_add_acq (__futex, 1); \
359 /* If __result == 0, we succeeded in acquiring the lock. \
360 If __result == 1, we switched the lock to 'contended' state, which \
361 will cause a [possibly unnecessary] call to lll_futex_wait. This is \
362 unlikely, so we accept the possible inefficiency. \
363 If __result >= 2, we need to set the lock to 'contended' state to avoid \
364 unbounded increase from subsequent trylocks. */ \
366 __result = atomic_exchange_acq (__futex, 2); \
371 #endif /* lowlevellock.h */
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