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a5f2bd86 | 1 | /* Set current priority ceiling of pthread_mutex_t. |
2b778ceb | 2 | Copyright (C) 2006-2021 Free Software Foundation, Inc. |
a5f2bd86 RM |
3 | This file is part of the GNU C Library. |
4 | Contributed by Jakub Jelinek <jakub@redhat.com>, 2006. | |
5 | ||
6 | The GNU C Library is free software; you can redistribute it and/or | |
7 | modify it under the terms of the GNU Lesser General Public | |
8 | License as published by the Free Software Foundation; either | |
9 | version 2.1 of the License, or (at your option) any later version. | |
10 | ||
11 | The GNU C Library is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | Lesser General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU Lesser General Public | |
59ba27a6 | 17 | License along with the GNU C Library; if not, see |
5a82c748 | 18 | <https://www.gnu.org/licenses/>. */ |
a5f2bd86 | 19 | |
f17efcb4 | 20 | #include <stdbool.h> |
a5f2bd86 RM |
21 | #include <errno.h> |
22 | #include <pthreadP.h> | |
cdcb42d7 | 23 | #include <atomic.h> |
878fe624 | 24 | #include <futex-internal.h> |
a5f2bd86 RM |
25 | |
26 | ||
27 | int | |
f63f2bfd JM |
28 | pthread_mutex_setprioceiling (pthread_mutex_t *mutex, int prioceiling, |
29 | int *old_ceiling) | |
a5f2bd86 | 30 | { |
403b4feb SL |
31 | /* See concurrency notes regarding __kind in struct __pthread_mutex_s |
32 | in sysdeps/nptl/bits/thread-shared-types.h. */ | |
33 | if ((atomic_load_relaxed (&(mutex->__data.__kind)) | |
34 | & PTHREAD_MUTEX_PRIO_PROTECT_NP) == 0) | |
a5f2bd86 RM |
35 | return EINVAL; |
36 | ||
cdcb42d7 TR |
37 | /* See __init_sched_fifo_prio. */ |
38 | if (atomic_load_relaxed (&__sched_fifo_min_prio) == -1 | |
39 | || atomic_load_relaxed (&__sched_fifo_max_prio) == -1) | |
f17efcb4 UD |
40 | __init_sched_fifo_prio (); |
41 | ||
cdcb42d7 TR |
42 | if (__glibc_unlikely (prioceiling |
43 | < atomic_load_relaxed (&__sched_fifo_min_prio)) | |
44 | || __glibc_unlikely (prioceiling | |
45 | > atomic_load_relaxed (&__sched_fifo_max_prio)) | |
46 | || __glibc_unlikely ((prioceiling | |
f17efcb4 UD |
47 | & (PTHREAD_MUTEXATTR_PRIO_CEILING_MASK |
48 | >> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT)) | |
cdcb42d7 | 49 | != prioceiling)) |
a5f2bd86 RM |
50 | return EINVAL; |
51 | ||
f17efcb4 UD |
52 | /* Check whether we already hold the mutex. */ |
53 | bool locked = false; | |
5bd8a249 | 54 | int kind = PTHREAD_MUTEX_TYPE (mutex); |
f17efcb4 UD |
55 | if (mutex->__data.__owner == THREAD_GETMEM (THREAD_SELF, tid)) |
56 | { | |
5bd8a249 | 57 | if (kind == PTHREAD_MUTEX_PP_ERRORCHECK_NP) |
f17efcb4 UD |
58 | return EDEADLK; |
59 | ||
5bd8a249 | 60 | if (kind == PTHREAD_MUTEX_PP_RECURSIVE_NP) |
f17efcb4 UD |
61 | locked = true; |
62 | } | |
63 | ||
64 | int oldval = mutex->__data.__lock; | |
65 | if (! locked) | |
66 | do | |
67 | { | |
68 | /* Need to lock the mutex, but without obeying the priority | |
69 | protect protocol. */ | |
70 | int ceilval = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK); | |
71 | ||
72 | oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, | |
73 | ceilval | 1, ceilval); | |
74 | if (oldval == ceilval) | |
75 | break; | |
76 | ||
77 | do | |
78 | { | |
79 | oldval | |
80 | = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, | |
81 | ceilval | 2, | |
82 | ceilval | 1); | |
83 | ||
84 | if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval) | |
85 | break; | |
86 | ||
87 | if (oldval != ceilval) | |
878fe624 AZ |
88 | futex_wait ((unsigned int *) &mutex->__data.__lock, ceilval | 2, |
89 | PTHREAD_MUTEX_PSHARED (mutex)); | |
f17efcb4 UD |
90 | } |
91 | while (atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, | |
92 | ceilval | 2, ceilval) | |
93 | != ceilval); | |
94 | ||
95 | if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval) | |
96 | continue; | |
97 | } | |
98 | while (0); | |
99 | ||
100 | int oldprio = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) | |
101 | >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT; | |
102 | if (locked) | |
103 | { | |
104 | int ret = __pthread_tpp_change_priority (oldprio, prioceiling); | |
105 | if (ret) | |
106 | return ret; | |
107 | } | |
a5f2bd86 RM |
108 | |
109 | if (old_ceiling != NULL) | |
f17efcb4 | 110 | *old_ceiling = oldprio; |
a5f2bd86 | 111 | |
f17efcb4 UD |
112 | int newlock = 0; |
113 | if (locked) | |
114 | newlock = (mutex->__data.__lock & ~PTHREAD_MUTEX_PRIO_CEILING_MASK); | |
115 | mutex->__data.__lock = newlock | |
a5f2bd86 | 116 | | (prioceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT); |
f17efcb4 | 117 | atomic_full_barrier (); |
a5f2bd86 | 118 | |
b45b1c5b AZ |
119 | futex_wake ((unsigned int *)&mutex->__data.__lock, INT_MAX, |
120 | PTHREAD_MUTEX_PSHARED (mutex)); | |
a5f2bd86 RM |
121 | |
122 | return 0; | |
123 | } |