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a5f2bd86 | 1 | /* Set current priority ceiling of pthread_mutex_t. |
bfff8b1b | 2 | Copyright (C) 2006-2017 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 PE |
17 | License along with the GNU C Library; if not, see |
18 | <http://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> |
a5f2bd86 RM |
24 | |
25 | ||
26 | int | |
f63f2bfd JM |
27 | pthread_mutex_setprioceiling (pthread_mutex_t *mutex, int prioceiling, |
28 | int *old_ceiling) | |
a5f2bd86 RM |
29 | { |
30 | /* The low bits of __kind aren't ever changed after pthread_mutex_init, | |
31 | so we don't need a lock yet. */ | |
df47504c | 32 | if ((mutex->__data.__kind & PTHREAD_MUTEX_PRIO_PROTECT_NP) == 0) |
a5f2bd86 RM |
33 | return EINVAL; |
34 | ||
cdcb42d7 TR |
35 | /* See __init_sched_fifo_prio. */ |
36 | if (atomic_load_relaxed (&__sched_fifo_min_prio) == -1 | |
37 | || atomic_load_relaxed (&__sched_fifo_max_prio) == -1) | |
f17efcb4 UD |
38 | __init_sched_fifo_prio (); |
39 | ||
cdcb42d7 TR |
40 | if (__glibc_unlikely (prioceiling |
41 | < atomic_load_relaxed (&__sched_fifo_min_prio)) | |
42 | || __glibc_unlikely (prioceiling | |
43 | > atomic_load_relaxed (&__sched_fifo_max_prio)) | |
44 | || __glibc_unlikely ((prioceiling | |
f17efcb4 UD |
45 | & (PTHREAD_MUTEXATTR_PRIO_CEILING_MASK |
46 | >> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT)) | |
cdcb42d7 | 47 | != prioceiling)) |
a5f2bd86 RM |
48 | return EINVAL; |
49 | ||
f17efcb4 UD |
50 | /* Check whether we already hold the mutex. */ |
51 | bool locked = false; | |
5bd8a249 | 52 | int kind = PTHREAD_MUTEX_TYPE (mutex); |
f17efcb4 UD |
53 | if (mutex->__data.__owner == THREAD_GETMEM (THREAD_SELF, tid)) |
54 | { | |
5bd8a249 | 55 | if (kind == PTHREAD_MUTEX_PP_ERRORCHECK_NP) |
f17efcb4 UD |
56 | return EDEADLK; |
57 | ||
5bd8a249 | 58 | if (kind == PTHREAD_MUTEX_PP_RECURSIVE_NP) |
f17efcb4 UD |
59 | locked = true; |
60 | } | |
61 | ||
62 | int oldval = mutex->__data.__lock; | |
63 | if (! locked) | |
64 | do | |
65 | { | |
66 | /* Need to lock the mutex, but without obeying the priority | |
67 | protect protocol. */ | |
68 | int ceilval = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK); | |
69 | ||
70 | oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, | |
71 | ceilval | 1, ceilval); | |
72 | if (oldval == ceilval) | |
73 | break; | |
74 | ||
75 | do | |
76 | { | |
77 | oldval | |
78 | = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, | |
79 | ceilval | 2, | |
80 | ceilval | 1); | |
81 | ||
82 | if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval) | |
83 | break; | |
84 | ||
85 | if (oldval != ceilval) | |
835abc5c | 86 | lll_futex_wait (&mutex->__data.__lock, ceilval | 2, |
5bd8a249 | 87 | PTHREAD_MUTEX_PSHARED (mutex)); |
f17efcb4 UD |
88 | } |
89 | while (atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, | |
90 | ceilval | 2, ceilval) | |
91 | != ceilval); | |
92 | ||
93 | if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval) | |
94 | continue; | |
95 | } | |
96 | while (0); | |
97 | ||
98 | int oldprio = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) | |
99 | >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT; | |
100 | if (locked) | |
101 | { | |
102 | int ret = __pthread_tpp_change_priority (oldprio, prioceiling); | |
103 | if (ret) | |
104 | return ret; | |
105 | } | |
a5f2bd86 RM |
106 | |
107 | if (old_ceiling != NULL) | |
f17efcb4 | 108 | *old_ceiling = oldprio; |
a5f2bd86 | 109 | |
f17efcb4 UD |
110 | int newlock = 0; |
111 | if (locked) | |
112 | newlock = (mutex->__data.__lock & ~PTHREAD_MUTEX_PRIO_CEILING_MASK); | |
113 | mutex->__data.__lock = newlock | |
a5f2bd86 | 114 | | (prioceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT); |
f17efcb4 | 115 | atomic_full_barrier (); |
a5f2bd86 | 116 | |
835abc5c | 117 | lll_futex_wake (&mutex->__data.__lock, INT_MAX, |
5bd8a249 | 118 | PTHREAD_MUTEX_PSHARED (mutex)); |
a5f2bd86 RM |
119 | |
120 | return 0; | |
121 | } |