1/* Copyright (C) 2002-2021 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
4
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.
9
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.
14
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/>. */
18
19#include <assert.h>
20#include <errno.h>
21#include <stdbool.h>
22#include <string.h>
23#include <kernel-features.h>
24#include "pthreadP.h"
25#include <atomic.h>
26#include <pthread-offsets.h>
27#include <futex-internal.h>
28#include <shlib-compat.h>
29
30#include <stap-probe.h>
31
32static const struct pthread_mutexattr default_mutexattr =
33 {
34 /* Default is a normal mutex, not shared between processes. */
35 .mutexkind = PTHREAD_MUTEX_NORMAL
36 };
37
38
39static bool
40prio_inherit_missing (void)
41{
42 static int tpi_supported;
43 if (__glibc_unlikely (atomic_load_relaxed (&tpi_supported) == 0))
44 {
45 int e = futex_unlock_pi (&(unsigned int){0}, 0);
46 atomic_store_relaxed (&tpi_supported, e == ENOSYS ? -1 : 1);
47 }
48 return __glibc_unlikely (tpi_supported < 0);
49}
50
51int
52___pthread_mutex_init (pthread_mutex_t *mutex,
53 const pthread_mutexattr_t *mutexattr)
54{
55 const struct pthread_mutexattr *imutexattr;
56
57 ASSERT_TYPE_SIZE (pthread_mutex_t, __SIZEOF_PTHREAD_MUTEX_T);
58
59 /* __kind is the only field where its offset should be checked to
60 avoid ABI breakage with static initializers. */
61 ASSERT_PTHREAD_INTERNAL_OFFSET (pthread_mutex_t, __data.__kind,
62 __PTHREAD_MUTEX_KIND_OFFSET);
63 ASSERT_PTHREAD_INTERNAL_MEMBER_SIZE (pthread_mutex_t, __data.__kind, int);
64
65 imutexattr = ((const struct pthread_mutexattr *) mutexattr
66 ?: &default_mutexattr);
67
68 /* Sanity checks. */
69 switch (__builtin_expect (imutexattr->mutexkind
70 & PTHREAD_MUTEXATTR_PROTOCOL_MASK,
71 PTHREAD_PRIO_NONE
72 << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT))
73 {
74 case PTHREAD_PRIO_NONE << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
75 break;
76
77 case PTHREAD_PRIO_INHERIT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
78 if (__glibc_unlikely (prio_inherit_missing ()))
79 return ENOTSUP;
80 break;
81
82 default:
83 /* XXX: For now we don't support robust priority protected mutexes. */
84 if (imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_ROBUST)
85 return ENOTSUP;
86 break;
87 }
88
89 /* Clear the whole variable. */
90 memset (mutex, '\0', __SIZEOF_PTHREAD_MUTEX_T);
91
92 /* Copy the values from the attribute. */
93 int mutex_kind = imutexattr->mutexkind & ~PTHREAD_MUTEXATTR_FLAG_BITS;
94
95 if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_ROBUST) != 0)
96 {
97#ifndef __ASSUME_SET_ROBUST_LIST
98 if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_PSHARED) != 0
99 && !__nptl_set_robust_list_avail)
100 return ENOTSUP;
101#endif
102
103 mutex_kind |= PTHREAD_MUTEX_ROBUST_NORMAL_NP;
104 }
105
106 switch (imutexattr->mutexkind & PTHREAD_MUTEXATTR_PROTOCOL_MASK)
107 {
108 case PTHREAD_PRIO_INHERIT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
109 mutex_kind |= PTHREAD_MUTEX_PRIO_INHERIT_NP;
110 break;
111
112 case PTHREAD_PRIO_PROTECT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
113 mutex_kind |= PTHREAD_MUTEX_PRIO_PROTECT_NP;
114
115 int ceiling = (imutexattr->mutexkind
116 & PTHREAD_MUTEXATTR_PRIO_CEILING_MASK)
117 >> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT;
118 if (! ceiling)
119 {
120 /* See __init_sched_fifo_prio. */
121 if (atomic_load_relaxed (&__sched_fifo_min_prio) == -1)
122 __init_sched_fifo_prio ();
123 if (ceiling < atomic_load_relaxed (&__sched_fifo_min_prio))
124 ceiling = atomic_load_relaxed (&__sched_fifo_min_prio);
125 }
126 mutex->__data.__lock = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
127 break;
128
129 default:
130 break;
131 }
132
133 /* The kernel when waking robust mutexes on exit never uses
134 FUTEX_PRIVATE_FLAG FUTEX_WAKE. */
135 if ((imutexattr->mutexkind & (PTHREAD_MUTEXATTR_FLAG_PSHARED
136 | PTHREAD_MUTEXATTR_FLAG_ROBUST)) != 0)
137 mutex_kind |= PTHREAD_MUTEX_PSHARED_BIT;
138
139 /* See concurrency notes regarding __kind in struct __pthread_mutex_s
140 in sysdeps/nptl/bits/thread-shared-types.h. */
141 atomic_store_relaxed (&(mutex->__data.__kind), mutex_kind);
142
143 /* Default values: mutex not used yet. */
144 // mutex->__count = 0; already done by memset
145 // mutex->__owner = 0; already done by memset
146 // mutex->__nusers = 0; already done by memset
147 // mutex->__spins = 0; already done by memset
148 // mutex->__next = NULL; already done by memset
149
150 LIBC_PROBE (mutex_init, 1, mutex);
151
152 return 0;
153}
154versioned_symbol (libpthread, ___pthread_mutex_init, pthread_mutex_init,
155 GLIBC_2_0);
156libc_hidden_ver (___pthread_mutex_init, __pthread_mutex_init)
157#ifndef SHARED
158strong_alias (___pthread_mutex_init, __pthread_mutex_init)
159#endif
160
161#if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)
162compat_symbol (libpthread, ___pthread_mutex_init, __pthread_mutex_init,
163 GLIBC_2_0);
164#endif
165