1/* Copyright (C) 2002-2017 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 <http://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
28#include <stap-probe.h>
29
30static const struct pthread_mutexattr default_mutexattr =
31 {
32 /* Default is a normal mutex, not shared between processes. */
33 .mutexkind = PTHREAD_MUTEX_NORMAL
34 };
35
36
37static bool
38prio_inherit_missing (void)
39{
40#ifdef __NR_futex
41 static int tpi_supported;
42 if (__glibc_unlikely (tpi_supported == 0))
43 {
44 int lock = 0;
45 INTERNAL_SYSCALL_DECL (err);
46 int ret = INTERNAL_SYSCALL (futex, err, 4, &lock, FUTEX_UNLOCK_PI, 0, 0);
47 assert (INTERNAL_SYSCALL_ERROR_P (ret, err));
48 tpi_supported = INTERNAL_SYSCALL_ERRNO (ret, err) == ENOSYS ? -1 : 1;
49 }
50 return __glibc_unlikely (tpi_supported < 0);
51#endif
52 return true;
53}
54
55int
56__pthread_mutex_init (pthread_mutex_t *mutex,
57 const pthread_mutexattr_t *mutexattr)
58{
59 const struct pthread_mutexattr *imutexattr;
60
61 assert (sizeof (pthread_mutex_t) <= __SIZEOF_PTHREAD_MUTEX_T);
62 ASSERT_PTHREAD_INTERNAL_OFFSET (pthread_mutex_t, __data.__nusers,
63 __PTHREAD_MUTEX_NUSERS_OFFSET);
64 ASSERT_PTHREAD_INTERNAL_OFFSET (pthread_mutex_t, __data.__kind,
65 __PTHREAD_MUTEX_KIND_OFFSET);
66 ASSERT_PTHREAD_INTERNAL_OFFSET (pthread_mutex_t, __data.__spins,
67 __PTHREAD_MUTEX_SPINS_OFFSET);
68#if __PTHREAD_MUTEX_LOCK_ELISION
69 ASSERT_PTHREAD_INTERNAL_OFFSET (pthread_mutex_t, __data.__elision,
70 __PTHREAD_MUTEX_ELISION_OFFSET);
71#endif
72 ASSERT_PTHREAD_INTERNAL_OFFSET (pthread_mutex_t, __data.__list,
73 __PTHREAD_MUTEX_LIST_OFFSET);
74
75 imutexattr = ((const struct pthread_mutexattr *) mutexattr
76 ?: &default_mutexattr);
77
78 /* Sanity checks. */
79 switch (__builtin_expect (imutexattr->mutexkind
80 & PTHREAD_MUTEXATTR_PROTOCOL_MASK,
81 PTHREAD_PRIO_NONE
82 << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT))
83 {
84 case PTHREAD_PRIO_NONE << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
85 break;
86
87 case PTHREAD_PRIO_INHERIT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
88 if (__glibc_unlikely (prio_inherit_missing ()))
89 return ENOTSUP;
90 break;
91
92 default:
93 /* XXX: For now we don't support robust priority protected mutexes. */
94 if (imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_ROBUST)
95 return ENOTSUP;
96 break;
97 }
98
99 /* Clear the whole variable. */
100 memset (mutex, '\0', __SIZEOF_PTHREAD_MUTEX_T);
101
102 /* Copy the values from the attribute. */
103 mutex->__data.__kind = imutexattr->mutexkind & ~PTHREAD_MUTEXATTR_FLAG_BITS;
104
105 if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_ROBUST) != 0)
106 {
107#ifndef __ASSUME_SET_ROBUST_LIST
108 if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_PSHARED) != 0
109 && __set_robust_list_avail < 0)
110 return ENOTSUP;
111#endif
112
113 mutex->__data.__kind |= PTHREAD_MUTEX_ROBUST_NORMAL_NP;
114 }
115
116 switch (imutexattr->mutexkind & PTHREAD_MUTEXATTR_PROTOCOL_MASK)
117 {
118 case PTHREAD_PRIO_INHERIT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
119 mutex->__data.__kind |= PTHREAD_MUTEX_PRIO_INHERIT_NP;
120 break;
121
122 case PTHREAD_PRIO_PROTECT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
123 mutex->__data.__kind |= PTHREAD_MUTEX_PRIO_PROTECT_NP;
124
125 int ceiling = (imutexattr->mutexkind
126 & PTHREAD_MUTEXATTR_PRIO_CEILING_MASK)
127 >> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT;
128 if (! ceiling)
129 {
130 /* See __init_sched_fifo_prio. */
131 if (atomic_load_relaxed (&__sched_fifo_min_prio) == -1)
132 __init_sched_fifo_prio ();
133 if (ceiling < atomic_load_relaxed (&__sched_fifo_min_prio))
134 ceiling = atomic_load_relaxed (&__sched_fifo_min_prio);
135 }
136 mutex->__data.__lock = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
137 break;
138
139 default:
140 break;
141 }
142
143 /* The kernel when waking robust mutexes on exit never uses
144 FUTEX_PRIVATE_FLAG FUTEX_WAKE. */
145 if ((imutexattr->mutexkind & (PTHREAD_MUTEXATTR_FLAG_PSHARED
146 | PTHREAD_MUTEXATTR_FLAG_ROBUST)) != 0)
147 mutex->__data.__kind |= PTHREAD_MUTEX_PSHARED_BIT;
148
149 /* Default values: mutex not used yet. */
150 // mutex->__count = 0; already done by memset
151 // mutex->__owner = 0; already done by memset
152 // mutex->__nusers = 0; already done by memset
153 // mutex->__spins = 0; already done by memset
154 // mutex->__next = NULL; already done by memset
155
156 LIBC_PROBE (mutex_init, 1, mutex);
157
158 return 0;
159}
160weak_alias (__pthread_mutex_init, pthread_mutex_init)
161hidden_def (__pthread_mutex_init)
162