about summary refs log tree commit diff
path: root/nptl/pthread_mutex_lock.c
blob: dd22567c71dbca4e5545e5cc611bc1081451ff50 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
/* Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include "pthreadP.h"
#include <lowlevellock.h>


#ifndef LLL_MUTEX_LOCK
# define LLL_MUTEX_LOCK(mutex) lll_mutex_lock (mutex)
# define LLL_MUTEX_TRYLOCK(mutex) lll_mutex_trylock (mutex)
# define LLL_ROBUST_MUTEX_LOCK(mutex, id) lll_robust_mutex_lock (mutex, id)
#endif


int
__pthread_mutex_lock (mutex)
     pthread_mutex_t *mutex;
{
  assert (sizeof (mutex->__size) >= sizeof (mutex->__data));

  int oldval;
  pid_t id = THREAD_GETMEM (THREAD_SELF, tid);

  int retval = 0;
  switch (__builtin_expect (mutex->__data.__kind, PTHREAD_MUTEX_TIMED_NP))
    {
      /* Recursive mutex.  */
    case PTHREAD_MUTEX_RECURSIVE_NP:
      /* Check whether we already hold the mutex.  */
      if (mutex->__data.__owner == id)
	{
	  /* Just bump the counter.  */
	  if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
	    /* Overflow of the counter.  */
	    return EAGAIN;

	  ++mutex->__data.__count;

	  return 0;
	}

      /* We have to get the mutex.  */
      LLL_MUTEX_LOCK (mutex->__data.__lock);

      assert (mutex->__data.__owner == 0);
      mutex->__data.__count = 1;
      break;

      /* Error checking mutex.  */
    case PTHREAD_MUTEX_ERRORCHECK_NP:
      /* Check whether we already hold the mutex.  */
      if (__builtin_expect (mutex->__data.__owner == id, 0))
	return EDEADLK;

      /* FALLTHROUGH */

    case PTHREAD_MUTEX_TIMED_NP:
    simple:
      /* Normal mutex.  */
      LLL_MUTEX_LOCK (mutex->__data.__lock);
      assert (mutex->__data.__owner == 0);
      break;

    case PTHREAD_MUTEX_ADAPTIVE_NP:
      if (! __is_smp)
	goto simple;

      if (LLL_MUTEX_TRYLOCK (mutex->__data.__lock) != 0)
	{
	  int cnt = 0;
	  int max_cnt = MIN (MAX_ADAPTIVE_COUNT,
			     mutex->__data.__spins * 2 + 10);
	  do
	    {
	      if (cnt++ >= max_cnt)
		{
		  LLL_MUTEX_LOCK (mutex->__data.__lock);
		  break;
		}

#ifdef BUSY_WAIT_NOP
	      BUSY_WAIT_NOP;
#endif
	    }
	  while (LLL_MUTEX_TRYLOCK (mutex->__data.__lock) != 0);

	  mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
	}
      assert (mutex->__data.__owner == 0);
      break;

    case PTHREAD_MUTEX_ROBUST_PRIVATE_RECURSIVE_NP:
    case PTHREAD_MUTEX_ROBUST_PRIVATE_ERRORCHECK_NP:
    case PTHREAD_MUTEX_ROBUST_PRIVATE_NP:
    case PTHREAD_MUTEX_ROBUST_PRIVATE_ADAPTIVE_NP:
      oldval = mutex->__data.__lock;
      do
	{
	  if ((oldval & FUTEX_OWNER_DIED) != 0)
	    {
	      /* The previous owner died.  Try locking the mutex.  */
	      int newval;
	      while ((newval
		      = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
							     id, oldval))
		     != oldval)
		{
		  if ((newval & FUTEX_OWNER_DIED) == 0)
		    goto normal;
		  oldval = newval;
		}

	      /* We got the mutex.  */
	      mutex->__data.__count = 1;
	      /* But it is inconsistent unless marked otherwise.  */
	      mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;

	      ENQUEUE_MUTEX (mutex);

	      /* Note that we deliberately exit here.  If we fall
		 through to the end of the function __nusers would be
		 incremented which is not correct because the old
		 owner has to be discounted.  If we are not supposed
		 to increment __nusers we actually have to decrement
		 it here.  */
#ifdef NO_INCR
	      --mutex->__data.__nusers;
#endif

	      return EOWNERDEAD;
	    }

	normal:
	  /* Check whether we already hold the mutex.  */
	  if (__builtin_expect ((mutex->__data.__lock & FUTEX_TID_MASK)
				== id, 0))
	    {
	      if (mutex->__data.__kind
		  == PTHREAD_MUTEX_ROBUST_PRIVATE_ERRORCHECK_NP)
		return EDEADLK;

	      if (mutex->__data.__kind
		  == PTHREAD_MUTEX_ROBUST_PRIVATE_RECURSIVE_NP)
		{
		  /* Just bump the counter.  */
		  if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
		    /* Overflow of the counter.  */
		    return EAGAIN;

		  ++mutex->__data.__count;

		  return 0;
		}
	    }

	  oldval = LLL_ROBUST_MUTEX_LOCK (mutex->__data.__lock, id);

	  if (__builtin_expect (mutex->__data.__owner
				== PTHREAD_MUTEX_NOTRECOVERABLE, 0))
	    {
	      /* This mutex is now not recoverable.  */
	      mutex->__data.__count = 0;
	      lll_mutex_unlock (mutex->__data.__lock);
	      return ENOTRECOVERABLE;
	    }
	}
      while ((oldval & FUTEX_OWNER_DIED) != 0);

      mutex->__data.__count = 1;
      ENQUEUE_MUTEX (mutex);
      break;

    default:
      /* Correct code cannot set any other type.  */
      return EINVAL;
    }

  /* Record the ownership.  */
  mutex->__data.__owner = id;
#ifndef NO_INCR
  ++mutex->__data.__nusers;
#endif

  return retval;
}
#ifndef __pthread_mutex_lock
strong_alias (__pthread_mutex_lock, pthread_mutex_lock)
strong_alias (__pthread_mutex_lock, __pthread_mutex_lock_internal)
#endif