summaryrefslogtreecommitdiff
path: root/nptl/pthread_mutex_setprioceiling.c
blob: 1be7471c919a123c4ad6749865db2b28e40a3f43 (plain)
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
/* Set current priority ceiling of pthread_mutex_t.
   Copyright (C) 2006-2015 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Jakub Jelinek <jakub@redhat.com>, 2006.

   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, see
   <http://www.gnu.org/licenses/>.  */

#include <stdbool.h>
#include <errno.h>
#include <pthreadP.h>
#include <atomic.h>


int
pthread_mutex_setprioceiling (mutex, prioceiling, old_ceiling)
     pthread_mutex_t *mutex;
     int prioceiling;
     int *old_ceiling;
{
  /* The low bits of __kind aren't ever changed after pthread_mutex_init,
     so we don't need a lock yet.  */
  if ((mutex->__data.__kind & PTHREAD_MUTEX_PRIO_PROTECT_NP) == 0)
    return EINVAL;

  /* See __init_sched_fifo_prio.  */
  if (atomic_load_relaxed (&__sched_fifo_min_prio) == -1
      || atomic_load_relaxed (&__sched_fifo_max_prio) == -1)
    __init_sched_fifo_prio ();

  if (__glibc_unlikely (prioceiling
			< atomic_load_relaxed (&__sched_fifo_min_prio))
      || __glibc_unlikely (prioceiling
			   > atomic_load_relaxed (&__sched_fifo_max_prio))
      || __glibc_unlikely ((prioceiling
			    & (PTHREAD_MUTEXATTR_PRIO_CEILING_MASK
			       >> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT))
			   != prioceiling))
    return EINVAL;

  /* Check whether we already hold the mutex.  */
  bool locked = false;
  int kind = PTHREAD_MUTEX_TYPE (mutex);
  if (mutex->__data.__owner == THREAD_GETMEM (THREAD_SELF, tid))
    {
      if (kind == PTHREAD_MUTEX_PP_ERRORCHECK_NP)
	return EDEADLK;

      if (kind == PTHREAD_MUTEX_PP_RECURSIVE_NP)
	locked = true;
    }

  int oldval = mutex->__data.__lock;
  if (! locked)
    do
      {
	/* Need to lock the mutex, but without obeying the priority
	   protect protocol.  */
	int ceilval = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK);

	oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
						      ceilval | 1, ceilval);
	if (oldval == ceilval)
	  break;

	do
	  {
	    oldval
	      = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
						     ceilval | 2,
						     ceilval | 1);

	    if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval)
	      break;

	    if (oldval != ceilval)
	      lll_futex_wait (&mutex->__data.__lock, ceilval | 2,
			      PTHREAD_MUTEX_PSHARED (mutex));
	  }
	while (atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
						    ceilval | 2, ceilval)
	       != ceilval);

	if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval)
	  continue;
      }
    while (0);

  int oldprio = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)
		>> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
  if (locked)
    {
      int ret = __pthread_tpp_change_priority (oldprio, prioceiling);
      if (ret)
	return ret;
    }

  if (old_ceiling != NULL)
    *old_ceiling = oldprio;

  int newlock = 0;
  if (locked)
    newlock = (mutex->__data.__lock & ~PTHREAD_MUTEX_PRIO_CEILING_MASK);
  mutex->__data.__lock = newlock
			 | (prioceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT);
  atomic_full_barrier ();

  lll_futex_wake (&mutex->__data.__lock, INT_MAX,
		  PTHREAD_MUTEX_PSHARED (mutex));

  return 0;
}