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