1 /* sem_wait -- wait on a semaphore.  Generic futex-using version.
2    Copyright (C) 2003, 2007 Free Software Foundation, Inc.
3    This file is part of the GNU C Library.
4    Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
5 
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.
10 
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.
15 
16    You should have received a copy of the GNU Lesser General Public
17    License along with the GNU C Library; if not, see
18    <http://www.gnu.org/licenses/>.  */
19 
20 #include <errno.h>
21 #include <sysdep.h>
22 #include <lowlevellock.h>
23 #include <internaltypes.h>
24 #include <semaphore.h>
25 
26 #include <pthreadP.h>
27 
28 
29 void
30 attribute_hidden
__sem_wait_cleanup(void * arg)31 __sem_wait_cleanup (void *arg)
32 {
33   struct sparc_new_sem *isem = (struct sparc_new_sem *) arg;
34 
35   if (__atomic_is_v9)
36     atomic_decrement (&isem->nwaiters);
37   else
38     {
39       __sparc32_atomic_do_lock24 (&isem->lock);
40       isem->nwaiters--;
41       __sparc32_atomic_do_unlock24 (&isem->lock);
42     }
43 }
44 
45 
46 int
sem_wait(sem_t * sem)47 sem_wait (sem_t *sem)
48 {
49   struct sparc_new_sem *isem = (struct sparc_new_sem *) sem;
50   int err;
51   int val;
52 
53   if (__atomic_is_v9)
54     val = atomic_decrement_if_positive (&isem->value);
55   else
56     {
57       __sparc32_atomic_do_lock24 (&isem->lock);
58       val = isem->value;
59       if (val > 0)
60 	isem->value = val - 1;
61       else
62 	isem->nwaiters++;
63       __sparc32_atomic_do_unlock24 (&isem->lock);
64     }
65 
66   if (val > 0)
67     return 0;
68 
69   if (__atomic_is_v9)
70     atomic_increment (&isem->nwaiters);
71   else
72     /* Already done above while still holding isem->lock.  */;
73 
74   pthread_cleanup_push (__sem_wait_cleanup, isem);
75 
76   while (1)
77     {
78       /* Enable asynchronous cancellation.  Required by the standard.  */
79       int oldtype = __pthread_enable_asynccancel ();
80 
81       err = lll_futex_wait (&isem->value, 0,
82 			    isem->private ^ FUTEX_PRIVATE_FLAG);
83 
84       /* Disable asynchronous cancellation.  */
85       __pthread_disable_asynccancel (oldtype);
86 
87       if (err != 0 && err != -EWOULDBLOCK)
88 	{
89 	  __set_errno (-err);
90 	  err = -1;
91 	  break;
92 	}
93 
94       if (__atomic_is_v9)
95 	val = atomic_decrement_if_positive (&isem->value);
96       else
97 	{
98 	  __sparc32_atomic_do_lock24 (&isem->lock);
99 	  val = isem->value;
100 	  if (val > 0)
101 	    isem->value = val - 1;
102 	  __sparc32_atomic_do_unlock24 (&isem->lock);
103 	}
104 
105       if (val > 0)
106 	{
107 	  err = 0;
108 	  break;
109 	}
110     }
111 
112   pthread_cleanup_pop (0);
113 
114   if (__atomic_is_v9)
115     atomic_decrement (&isem->nwaiters);
116   else
117     {
118       __sparc32_atomic_do_lock24 (&isem->lock);
119       isem->nwaiters--;
120       __sparc32_atomic_do_unlock24 (&isem->lock);
121     }
122 
123   return err;
124 }
125