1/* Copyright (C) 2002-2016 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# ifndef __ASSUME_FUTEX_LOCK_PI
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 false;
53#endif
54 return true;
55}
56
57int
58__pthread_mutex_init (pthread_mutex_t *mutex,
59 const pthread_mutexattr_t *mutexattr)
60{
61 const struct pthread_mutexattr *imutexattr;
62
63 assert (sizeof (pthread_mutex_t) <= __SIZEOF_PTHREAD_MUTEX_T);
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 mutex->__data.__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 && __set_robust_list_avail < 0)
100 return ENOTSUP;
101#endif
102
103 mutex->__data.__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->__data.__kind |= PTHREAD_MUTEX_PRIO_INHERIT_NP;
110 break;
111
112 case PTHREAD_PRIO_PROTECT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
113 mutex->__data.__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->__data.__kind |= PTHREAD_MUTEX_PSHARED_BIT;
138
139 /* Default values: mutex not used yet. */
140 // mutex->__count = 0; already done by memset
141 // mutex->__owner = 0; already done by memset
142 // mutex->__nusers = 0; already done by memset
143 // mutex->__spins = 0; already done by memset
144 // mutex->__next = NULL; already done by memset
145
146 LIBC_PROBE (mutex_init, 1, mutex);
147
148 return 0;
149}
150strong_alias (__pthread_mutex_init, pthread_mutex_init)
151hidden_def (__pthread_mutex_init)
152