Optimizations from GMP.
[glibc.git] / nptl / pthread_mutex_init.c
blobd9b1ef0b98d129ded2ebf256ea5d243406f3fdbc
1 /* Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007
2 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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.
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.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, write to the Free
18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
19 02111-1307 USA. */
21 #include <assert.h>
22 #include <errno.h>
23 #include <string.h>
24 #include <kernel-features.h>
25 #include "pthreadP.h"
27 static const struct pthread_mutexattr default_attr =
29 /* Default is a normal mutex, not shared between processes. */
30 .mutexkind = PTHREAD_MUTEX_NORMAL
34 #ifndef __ASSUME_FUTEX_LOCK_PI
35 static int tpi_supported;
36 #endif
39 int
40 __pthread_mutex_init (mutex, mutexattr)
41 pthread_mutex_t *mutex;
42 const pthread_mutexattr_t *mutexattr;
44 const struct pthread_mutexattr *imutexattr;
46 assert (sizeof (pthread_mutex_t) <= __SIZEOF_PTHREAD_MUTEX_T);
48 imutexattr = (const struct pthread_mutexattr *) mutexattr ?: &default_attr;
50 /* Sanity checks. */
51 switch (__builtin_expect (imutexattr->mutexkind
52 & PTHREAD_MUTEXATTR_PROTOCOL_MASK,
53 PTHREAD_PRIO_NONE
54 << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT))
56 case PTHREAD_PRIO_NONE << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
57 break;
59 case PTHREAD_PRIO_INHERIT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
60 #ifndef __ASSUME_FUTEX_LOCK_PI
61 if (__builtin_expect (tpi_supported == 0, 0))
63 int lock = 0;
64 INTERNAL_SYSCALL_DECL (err);
65 int ret = INTERNAL_SYSCALL (futex, err, 4, &lock, FUTEX_UNLOCK_PI,
66 0, 0);
67 assert (INTERNAL_SYSCALL_ERROR_P (ret, err));
68 tpi_supported = INTERNAL_SYSCALL_ERRNO (ret, err) == ENOSYS ? -1 : 1;
70 if (__builtin_expect (tpi_supported < 0, 0))
71 return ENOTSUP;
72 #endif
73 break;
75 default:
76 /* XXX: For now we don't support robust priority protected mutexes. */
77 if (imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_ROBUST)
78 return ENOTSUP;
79 break;
82 /* Clear the whole variable. */
83 memset (mutex, '\0', __SIZEOF_PTHREAD_MUTEX_T);
85 /* Copy the values from the attribute. */
86 mutex->__data.__kind = imutexattr->mutexkind & ~PTHREAD_MUTEXATTR_FLAG_BITS;
88 if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_ROBUST) != 0)
90 #ifndef __ASSUME_SET_ROBUST_LIST
91 if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_PSHARED) != 0
92 && __set_robust_list_avail < 0)
93 return ENOTSUP;
94 #endif
96 mutex->__data.__kind |= PTHREAD_MUTEX_ROBUST_NORMAL_NP;
99 switch (imutexattr->mutexkind & PTHREAD_MUTEXATTR_PROTOCOL_MASK)
101 case PTHREAD_PRIO_INHERIT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
102 mutex->__data.__kind |= PTHREAD_MUTEX_PRIO_INHERIT_NP;
103 break;
105 case PTHREAD_PRIO_PROTECT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
106 mutex->__data.__kind |= PTHREAD_MUTEX_PRIO_PROTECT_NP;
108 int ceiling = (imutexattr->mutexkind
109 & PTHREAD_MUTEXATTR_PRIO_CEILING_MASK)
110 >> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT;
111 if (! ceiling)
113 if (__sched_fifo_min_prio == -1)
114 __init_sched_fifo_prio ();
115 if (ceiling < __sched_fifo_min_prio)
116 ceiling = __sched_fifo_min_prio;
118 mutex->__data.__lock = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
119 break;
121 default:
122 break;
125 /* The kernel when waking robust mutexes on exit never uses
126 FUTEX_PRIVATE_FLAG FUTEX_WAKE. */
127 if ((imutexattr->mutexkind & (PTHREAD_MUTEXATTR_FLAG_PSHARED
128 | PTHREAD_MUTEXATTR_FLAG_ROBUST)) != 0)
129 mutex->__data.__kind |= PTHREAD_MUTEX_PSHARED_BIT;
131 /* Default values: mutex not used yet. */
132 // mutex->__count = 0; already done by memset
133 // mutex->__owner = 0; already done by memset
134 // mutex->__nusers = 0; already done by memset
135 // mutex->__spins = 0; already done by memset
136 // mutex->__next = NULL; already done by memset
138 return 0;
140 strong_alias (__pthread_mutex_init, pthread_mutex_init)
141 INTDEF(__pthread_mutex_init)