1 /* Copyright (C) 2002-2020 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
22 #include <sys/param.h>
26 #include <lowlevellock.h>
27 #include <not-cancel.h>
28 #include <futex-internal.h>
30 #include <stap-probe.h>
32 #ifndef lll_clocklock_elision
33 #define lll_clocklock_elision(futex, adapt_count, clockid, abstime, private) \
34 lll_clocklock (futex, clockid, abstime, private)
37 #ifndef lll_trylock_elision
38 #define lll_trylock_elision(a,t) lll_trylock(a)
42 #define FORCE_ELISION(m, s)
46 __pthread_mutex_clocklock_common (pthread_mutex_t
*mutex
,
48 const struct timespec
*abstime
)
51 pid_t id
= THREAD_GETMEM (THREAD_SELF
, tid
);
54 /* We must not check ABSTIME here. If the thread does not block
55 abstime must not be checked for a valid value. */
57 /* See concurrency notes regarding mutex type which is loaded from __kind
58 in struct __pthread_mutex_s in sysdeps/nptl/bits/thread-shared-types.h. */
59 switch (__builtin_expect (PTHREAD_MUTEX_TYPE_ELISION (mutex
),
60 PTHREAD_MUTEX_TIMED_NP
))
62 /* Recursive mutex. */
63 case PTHREAD_MUTEX_RECURSIVE_NP
|PTHREAD_MUTEX_ELISION_NP
:
64 case PTHREAD_MUTEX_RECURSIVE_NP
:
65 /* Check whether we already hold the mutex. */
66 if (mutex
->__data
.__owner
== id
)
68 /* Just bump the counter. */
69 if (__glibc_unlikely (mutex
->__data
.__count
+ 1 == 0))
70 /* Overflow of the counter. */
73 ++mutex
->__data
.__count
;
78 /* We have to get the mutex. */
79 result
= lll_clocklock (mutex
->__data
.__lock
, clockid
, abstime
,
80 PTHREAD_MUTEX_PSHARED (mutex
));
85 /* Only locked once so far. */
86 mutex
->__data
.__count
= 1;
89 /* Error checking mutex. */
90 case PTHREAD_MUTEX_ERRORCHECK_NP
:
91 /* Check whether we already hold the mutex. */
92 if (__glibc_unlikely (mutex
->__data
.__owner
== id
))
95 /* Don't do lock elision on an error checking mutex. */
98 case PTHREAD_MUTEX_TIMED_NP
:
99 FORCE_ELISION (mutex
, goto elision
);
102 result
= lll_clocklock (mutex
->__data
.__lock
, clockid
, abstime
,
103 PTHREAD_MUTEX_PSHARED (mutex
));
106 case PTHREAD_MUTEX_TIMED_ELISION_NP
:
107 elision
: __attribute__((unused
))
108 /* Don't record ownership */
109 return lll_clocklock_elision (mutex
->__data
.__lock
,
110 mutex
->__data
.__spins
,
112 PTHREAD_MUTEX_PSHARED (mutex
));
115 case PTHREAD_MUTEX_ADAPTIVE_NP
:
119 if (lll_trylock (mutex
->__data
.__lock
) != 0)
122 int max_cnt
= MIN (max_adaptive_count (),
123 mutex
->__data
.__spins
* 2 + 10);
126 if (cnt
++ >= max_cnt
)
128 result
= lll_clocklock (mutex
->__data
.__lock
,
130 PTHREAD_MUTEX_PSHARED (mutex
));
135 while (lll_trylock (mutex
->__data
.__lock
) != 0);
137 mutex
->__data
.__spins
+= (cnt
- mutex
->__data
.__spins
) / 8;
141 case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP
:
142 case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP
:
143 case PTHREAD_MUTEX_ROBUST_NORMAL_NP
:
144 case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP
:
145 THREAD_SETMEM (THREAD_SELF
, robust_head
.list_op_pending
,
146 &mutex
->__data
.__list
.__next
);
147 /* We need to set op_pending before starting the operation. Also
148 see comments at ENQUEUE_MUTEX. */
149 __asm ("" ::: "memory");
151 oldval
= mutex
->__data
.__lock
;
152 /* This is set to FUTEX_WAITERS iff we might have shared the
153 FUTEX_WAITERS flag with other threads, and therefore need to keep it
154 set to avoid lost wake-ups. We have the same requirement in the
155 simple mutex algorithm. */
156 unsigned int assume_other_futex_waiters
= 0;
159 /* Try to acquire the lock through a CAS from 0 (not acquired) to
160 our TID | assume_other_futex_waiters. */
161 if (__glibc_likely (oldval
== 0))
164 = atomic_compare_and_exchange_val_acq (&mutex
->__data
.__lock
,
165 id
| assume_other_futex_waiters
, 0);
166 if (__glibc_likely (oldval
== 0))
170 if ((oldval
& FUTEX_OWNER_DIED
) != 0)
172 /* The previous owner died. Try locking the mutex. */
173 int newval
= id
| (oldval
& FUTEX_WAITERS
)
174 | assume_other_futex_waiters
;
177 = atomic_compare_and_exchange_val_acq (&mutex
->__data
.__lock
,
179 if (newval
!= oldval
)
185 /* We got the mutex. */
186 mutex
->__data
.__count
= 1;
187 /* But it is inconsistent unless marked otherwise. */
188 mutex
->__data
.__owner
= PTHREAD_MUTEX_INCONSISTENT
;
190 /* We must not enqueue the mutex before we have acquired it.
191 Also see comments at ENQUEUE_MUTEX. */
192 __asm ("" ::: "memory");
193 ENQUEUE_MUTEX (mutex
);
194 /* We need to clear op_pending after we enqueue the mutex. */
195 __asm ("" ::: "memory");
196 THREAD_SETMEM (THREAD_SELF
, robust_head
.list_op_pending
, NULL
);
198 /* Note that we deliberately exit here. If we fall
199 through to the end of the function __nusers would be
200 incremented which is not correct because the old
201 owner has to be discounted. */
205 /* Check whether we already hold the mutex. */
206 if (__glibc_unlikely ((oldval
& FUTEX_TID_MASK
) == id
))
208 int kind
= PTHREAD_MUTEX_TYPE (mutex
);
209 if (kind
== PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP
)
211 /* We do not need to ensure ordering wrt another memory
212 access. Also see comments at ENQUEUE_MUTEX. */
213 THREAD_SETMEM (THREAD_SELF
, robust_head
.list_op_pending
,
218 if (kind
== PTHREAD_MUTEX_ROBUST_RECURSIVE_NP
)
220 /* We do not need to ensure ordering wrt another memory
222 THREAD_SETMEM (THREAD_SELF
, robust_head
.list_op_pending
,
225 /* Just bump the counter. */
226 if (__glibc_unlikely (mutex
->__data
.__count
+ 1 == 0))
227 /* Overflow of the counter. */
230 ++mutex
->__data
.__count
;
232 LIBC_PROBE (mutex_timedlock_acquired
, 1, mutex
);
238 /* We are about to block; check whether the timeout is invalid. */
239 if (! valid_nanoseconds (abstime
->tv_nsec
))
241 /* Work around the fact that the kernel rejects negative timeout
242 values despite them being valid. */
243 if (__glibc_unlikely (abstime
->tv_sec
< 0))
246 /* We cannot acquire the mutex nor has its owner died. Thus, try
247 to block using futexes. Set FUTEX_WAITERS if necessary so that
248 other threads are aware that there are potentially threads
249 blocked on the futex. Restart if oldval changed in the
251 if ((oldval
& FUTEX_WAITERS
) == 0)
253 if (atomic_compare_and_exchange_bool_acq (&mutex
->__data
.__lock
,
254 oldval
| FUTEX_WAITERS
,
258 oldval
= mutex
->__data
.__lock
;
261 oldval
|= FUTEX_WAITERS
;
264 /* It is now possible that we share the FUTEX_WAITERS flag with
265 another thread; therefore, update assume_other_futex_waiters so
266 that we do not forget about this when handling other cases
267 above and thus do not cause lost wake-ups. */
268 assume_other_futex_waiters
|= FUTEX_WAITERS
;
270 /* Block using the futex. */
271 int err
= lll_futex_clock_wait_bitset (&mutex
->__data
.__lock
,
272 oldval
, clockid
, abstime
,
273 PTHREAD_ROBUST_MUTEX_PSHARED (mutex
));
274 /* The futex call timed out. */
275 if (err
== -ETIMEDOUT
)
277 /* Reload current lock value. */
278 oldval
= mutex
->__data
.__lock
;
281 /* We have acquired the mutex; check if it is still consistent. */
282 if (__builtin_expect (mutex
->__data
.__owner
283 == PTHREAD_MUTEX_NOTRECOVERABLE
, 0))
285 /* This mutex is now not recoverable. */
286 mutex
->__data
.__count
= 0;
287 int private = PTHREAD_ROBUST_MUTEX_PSHARED (mutex
);
288 lll_unlock (mutex
->__data
.__lock
, private);
289 /* FIXME This violates the mutex destruction requirements. See
290 __pthread_mutex_unlock_full. */
291 THREAD_SETMEM (THREAD_SELF
, robust_head
.list_op_pending
, NULL
);
292 return ENOTRECOVERABLE
;
295 mutex
->__data
.__count
= 1;
296 /* We must not enqueue the mutex before we have acquired it.
297 Also see comments at ENQUEUE_MUTEX. */
298 __asm ("" ::: "memory");
299 ENQUEUE_MUTEX (mutex
);
300 /* We need to clear op_pending after we enqueue the mutex. */
301 __asm ("" ::: "memory");
302 THREAD_SETMEM (THREAD_SELF
, robust_head
.list_op_pending
, NULL
);
305 /* The PI support requires the Linux futex system call. If that's not
306 available, pthread_mutex_init should never have allowed the type to
307 be set. So it will get the default case for an invalid type. */
309 case PTHREAD_MUTEX_PI_RECURSIVE_NP
:
310 case PTHREAD_MUTEX_PI_ERRORCHECK_NP
:
311 case PTHREAD_MUTEX_PI_NORMAL_NP
:
312 case PTHREAD_MUTEX_PI_ADAPTIVE_NP
:
313 case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP
:
314 case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP
:
315 case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP
:
316 case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP
:
320 /* See concurrency notes regarding __kind in struct __pthread_mutex_s
321 in sysdeps/nptl/bits/thread-shared-types.h. */
322 int mutex_kind
= atomic_load_relaxed (&(mutex
->__data
.__kind
));
323 kind
= mutex_kind
& PTHREAD_MUTEX_KIND_MASK_NP
;
324 robust
= mutex_kind
& PTHREAD_MUTEX_ROBUST_NORMAL_NP
;
329 /* Note: robust PI futexes are signaled by setting bit 0. */
330 THREAD_SETMEM (THREAD_SELF
, robust_head
.list_op_pending
,
331 (void *) (((uintptr_t) &mutex
->__data
.__list
.__next
)
333 /* We need to set op_pending before starting the operation. Also
334 see comments at ENQUEUE_MUTEX. */
335 __asm ("" ::: "memory");
338 oldval
= mutex
->__data
.__lock
;
340 /* Check whether we already hold the mutex. */
341 if (__glibc_unlikely ((oldval
& FUTEX_TID_MASK
) == id
))
343 if (kind
== PTHREAD_MUTEX_ERRORCHECK_NP
)
345 /* We do not need to ensure ordering wrt another memory
347 THREAD_SETMEM (THREAD_SELF
, robust_head
.list_op_pending
, NULL
);
351 if (kind
== PTHREAD_MUTEX_RECURSIVE_NP
)
353 /* We do not need to ensure ordering wrt another memory
355 THREAD_SETMEM (THREAD_SELF
, robust_head
.list_op_pending
, NULL
);
357 /* Just bump the counter. */
358 if (__glibc_unlikely (mutex
->__data
.__count
+ 1 == 0))
359 /* Overflow of the counter. */
362 ++mutex
->__data
.__count
;
364 LIBC_PROBE (mutex_timedlock_acquired
, 1, mutex
);
370 oldval
= atomic_compare_and_exchange_val_acq (&mutex
->__data
.__lock
,
375 /* The mutex is locked. The kernel will now take care of
376 everything. The timeout value must be a relative value.
378 int private = (robust
379 ? PTHREAD_ROBUST_MUTEX_PSHARED (mutex
)
380 : PTHREAD_MUTEX_PSHARED (mutex
));
381 int e
= futex_lock_pi ((unsigned int *) &mutex
->__data
.__lock
,
385 else if (e
== ESRCH
|| e
== EDEADLK
)
388 || (kind
!= PTHREAD_MUTEX_ERRORCHECK_NP
389 && kind
!= PTHREAD_MUTEX_RECURSIVE_NP
));
390 /* ESRCH can happen only for non-robust PI mutexes where
391 the owner of the lock died. */
392 assert (e
!= ESRCH
|| !robust
);
394 /* Delay the thread until the timeout is reached. Then return
397 e
= lll_timedwait (&(int){0}, 0, clockid
, abstime
,
399 while (e
!= ETIMEDOUT
);
405 oldval
= mutex
->__data
.__lock
;
407 assert (robust
|| (oldval
& FUTEX_OWNER_DIED
) == 0);
410 if (__glibc_unlikely (oldval
& FUTEX_OWNER_DIED
))
412 atomic_and (&mutex
->__data
.__lock
, ~FUTEX_OWNER_DIED
);
414 /* We got the mutex. */
415 mutex
->__data
.__count
= 1;
416 /* But it is inconsistent unless marked otherwise. */
417 mutex
->__data
.__owner
= PTHREAD_MUTEX_INCONSISTENT
;
419 /* We must not enqueue the mutex before we have acquired it.
420 Also see comments at ENQUEUE_MUTEX. */
421 __asm ("" ::: "memory");
422 ENQUEUE_MUTEX_PI (mutex
);
423 /* We need to clear op_pending after we enqueue the mutex. */
424 __asm ("" ::: "memory");
425 THREAD_SETMEM (THREAD_SELF
, robust_head
.list_op_pending
, NULL
);
427 /* Note that we deliberately exit here. If we fall
428 through to the end of the function __nusers would be
429 incremented which is not correct because the old owner
430 has to be discounted. */
435 && __builtin_expect (mutex
->__data
.__owner
436 == PTHREAD_MUTEX_NOTRECOVERABLE
, 0))
438 /* This mutex is now not recoverable. */
439 mutex
->__data
.__count
= 0;
441 futex_unlock_pi ((unsigned int *) &mutex
->__data
.__lock
,
442 PTHREAD_ROBUST_MUTEX_PSHARED (mutex
));
444 /* To the kernel, this will be visible after the kernel has
445 acquired the mutex in the syscall. */
446 THREAD_SETMEM (THREAD_SELF
, robust_head
.list_op_pending
, NULL
);
447 return ENOTRECOVERABLE
;
450 mutex
->__data
.__count
= 1;
453 /* We must not enqueue the mutex before we have acquired it.
454 Also see comments at ENQUEUE_MUTEX. */
455 __asm ("" ::: "memory");
456 ENQUEUE_MUTEX_PI (mutex
);
457 /* We need to clear op_pending after we enqueue the mutex. */
458 __asm ("" ::: "memory");
459 THREAD_SETMEM (THREAD_SELF
, robust_head
.list_op_pending
, NULL
);
463 #endif /* __NR_futex. */
465 case PTHREAD_MUTEX_PP_RECURSIVE_NP
:
466 case PTHREAD_MUTEX_PP_ERRORCHECK_NP
:
467 case PTHREAD_MUTEX_PP_NORMAL_NP
:
468 case PTHREAD_MUTEX_PP_ADAPTIVE_NP
:
470 /* See concurrency notes regarding __kind in struct __pthread_mutex_s
471 in sysdeps/nptl/bits/thread-shared-types.h. */
472 int kind
= atomic_load_relaxed (&(mutex
->__data
.__kind
))
473 & PTHREAD_MUTEX_KIND_MASK_NP
;
475 oldval
= mutex
->__data
.__lock
;
477 /* Check whether we already hold the mutex. */
478 if (mutex
->__data
.__owner
== id
)
480 if (kind
== PTHREAD_MUTEX_ERRORCHECK_NP
)
483 if (kind
== PTHREAD_MUTEX_RECURSIVE_NP
)
485 /* Just bump the counter. */
486 if (__glibc_unlikely (mutex
->__data
.__count
+ 1 == 0))
487 /* Overflow of the counter. */
490 ++mutex
->__data
.__count
;
492 LIBC_PROBE (mutex_timedlock_acquired
, 1, mutex
);
498 int oldprio
= -1, ceilval
;
501 int ceiling
= (oldval
& PTHREAD_MUTEX_PRIO_CEILING_MASK
)
502 >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT
;
504 if (__pthread_current_priority () > ceiling
)
509 __pthread_tpp_change_priority (oldprio
, -1);
513 result
= __pthread_tpp_change_priority (oldprio
, ceiling
);
517 ceilval
= ceiling
<< PTHREAD_MUTEX_PRIO_CEILING_SHIFT
;
521 = atomic_compare_and_exchange_val_acq (&mutex
->__data
.__lock
,
522 ceilval
| 1, ceilval
);
524 if (oldval
== ceilval
)
530 = atomic_compare_and_exchange_val_acq (&mutex
->__data
.__lock
,
534 if ((oldval
& PTHREAD_MUTEX_PRIO_CEILING_MASK
) != ceilval
)
537 if (oldval
!= ceilval
)
539 /* Reject invalid timeouts. */
540 if (! valid_nanoseconds (abstime
->tv_nsec
))
548 /* Get the current time. */
549 __clock_gettime (CLOCK_REALTIME
, &rt
);
551 /* Compute relative timeout. */
552 rt
.tv_sec
= abstime
->tv_sec
- rt
.tv_sec
;
553 rt
.tv_nsec
= abstime
->tv_nsec
- rt
.tv_nsec
;
556 rt
.tv_nsec
+= 1000000000;
560 /* Already timed out? */
567 lll_futex_timed_wait (&mutex
->__data
.__lock
,
569 PTHREAD_MUTEX_PSHARED (mutex
));
572 while (atomic_compare_and_exchange_val_acq (&mutex
->__data
.__lock
,
573 ceilval
| 2, ceilval
)
576 while ((oldval
& PTHREAD_MUTEX_PRIO_CEILING_MASK
) != ceilval
);
578 assert (mutex
->__data
.__owner
== 0);
579 mutex
->__data
.__count
= 1;
584 /* Correct code cannot set any other type. */
590 /* Record the ownership. */
591 mutex
->__data
.__owner
= id
;
592 ++mutex
->__data
.__nusers
;
594 LIBC_PROBE (mutex_timedlock_acquired
, 1, mutex
);
602 __pthread_mutex_clocklock (pthread_mutex_t
*mutex
,
604 const struct timespec
*abstime
)
606 if (__glibc_unlikely (!lll_futex_supported_clockid (clockid
)))
609 LIBC_PROBE (mutex_clocklock_entry
, 3, mutex
, clockid
, abstime
);
610 return __pthread_mutex_clocklock_common (mutex
, clockid
, abstime
);
612 weak_alias (__pthread_mutex_clocklock
, pthread_mutex_clocklock
)
615 __pthread_mutex_timedlock (pthread_mutex_t
*mutex
,
616 const struct timespec
*abstime
)
618 LIBC_PROBE (mutex_timedlock_entry
, 2, mutex
, abstime
);
619 return __pthread_mutex_clocklock_common (mutex
, CLOCK_REALTIME
, abstime
);
621 weak_alias (__pthread_mutex_timedlock
, pthread_mutex_timedlock
)