File: tpp.c

package info (click to toggle)
glibc 2.24-11+deb9u4
  • links: PTS, VCS
  • area: main
  • in suites: stretch, stretch-proposed-updates
  • size: 225,852 kB
  • sloc: ansic: 996,505; asm: 261,827; sh: 10,484; makefile: 9,856; cpp: 4,169; python: 3,971; perl: 2,254; awk: 1,753; pascal: 1,521; yacc: 291; sed: 80
file content (195 lines) | stat: -rw-r--r-- 5,693 bytes parent folder | download
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
/* Thread Priority Protect helpers.
   Copyright (C) 2006-2016 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 <assert.h>
#include <atomic.h>
#include <errno.h>
#include <pthreadP.h>
#include <sched.h>
#include <stdlib.h>
#include <atomic.h>


int __sched_fifo_min_prio = -1;
int __sched_fifo_max_prio = -1;

/* We only want to initialize __sched_fifo_min_prio and __sched_fifo_max_prio
   once.  The standard solution would be similar to pthread_once, but then
   readers would need to use an acquire fence.  In this specific case,
   initialization is comprised of just idempotent writes to two variables
   that have an initial value of -1.  Therefore, we can treat each variable as
   a separate, at-least-once initialized value.  This enables using just
   relaxed MO loads and stores, but requires that consumers check for
   initialization of each value that is to be used; see
   __pthread_tpp_change_priority for an example.
 */
void
__init_sched_fifo_prio (void)
{
  atomic_store_relaxed (&__sched_fifo_max_prio,
			sched_get_priority_max (SCHED_FIFO));
  atomic_store_relaxed (&__sched_fifo_min_prio,
			sched_get_priority_min (SCHED_FIFO));
}

int
__pthread_tpp_change_priority (int previous_prio, int new_prio)
{
  struct pthread *self = THREAD_SELF;
  struct priority_protection_data *tpp = THREAD_GETMEM (self, tpp);
  int fifo_min_prio = atomic_load_relaxed (&__sched_fifo_min_prio);
  int fifo_max_prio = atomic_load_relaxed (&__sched_fifo_max_prio);

  if (tpp == NULL)
    {
      /* See __init_sched_fifo_prio.  We need both the min and max prio,
         so need to check both, and run initialization if either one is
         not initialized.  The memory model's write-read coherence rule
         makes this work.  */
      if (fifo_min_prio == -1 || fifo_max_prio == -1)
	{
	  __init_sched_fifo_prio ();
	  fifo_min_prio = atomic_load_relaxed (&__sched_fifo_min_prio);
	  fifo_max_prio = atomic_load_relaxed (&__sched_fifo_max_prio);
	}

      size_t size = sizeof *tpp;
      size += (fifo_max_prio - fifo_min_prio + 1)
	      * sizeof (tpp->priomap[0]);
      tpp = calloc (size, 1);
      if (tpp == NULL)
	return ENOMEM;
      tpp->priomax = fifo_min_prio - 1;
      THREAD_SETMEM (self, tpp, tpp);
    }

  assert (new_prio == -1
	  || (new_prio >= fifo_min_prio
	      && new_prio <= fifo_max_prio));
  assert (previous_prio == -1
	  || (previous_prio >= fifo_min_prio
	      && previous_prio <= fifo_max_prio));

  int priomax = tpp->priomax;
  int newpriomax = priomax;
  if (new_prio != -1)
    {
      if (tpp->priomap[new_prio - fifo_min_prio] + 1 == 0)
	return EAGAIN;
      ++tpp->priomap[new_prio - fifo_min_prio];
      if (new_prio > priomax)
	newpriomax = new_prio;
    }

  if (previous_prio != -1)
    {
      if (--tpp->priomap[previous_prio - fifo_min_prio] == 0
	  && priomax == previous_prio
	  && previous_prio > new_prio)
	{
	  int i;
	  for (i = previous_prio - 1; i >= fifo_min_prio; --i)
	    if (tpp->priomap[i - fifo_min_prio])
	      break;
	  newpriomax = i;
	}
    }

  if (priomax == newpriomax)
    return 0;

  /* See CREATE THREAD NOTES in nptl/pthread_create.c.  */
  lll_lock (self->lock, LLL_PRIVATE);

  tpp->priomax = newpriomax;

  int result = 0;

  if ((self->flags & ATTR_FLAG_SCHED_SET) == 0)
    {
      if (__sched_getparam (self->tid, &self->schedparam) != 0)
	result = errno;
      else
	self->flags |= ATTR_FLAG_SCHED_SET;
    }

  if ((self->flags & ATTR_FLAG_POLICY_SET) == 0)
    {
      self->schedpolicy = __sched_getscheduler (self->tid);
      if (self->schedpolicy == -1)
	result = errno;
      else
	self->flags |= ATTR_FLAG_POLICY_SET;
    }

  if (result == 0)
    {
      struct sched_param sp = self->schedparam;
      if (sp.sched_priority < newpriomax || sp.sched_priority < priomax)
	{
	  if (sp.sched_priority < newpriomax)
	    sp.sched_priority = newpriomax;

	  if (__sched_setscheduler (self->tid, self->schedpolicy, &sp) < 0)
	    result = errno;
	}
    }

  lll_unlock (self->lock, LLL_PRIVATE);

  return result;
}

int
__pthread_current_priority (void)
{
  struct pthread *self = THREAD_SELF;
  if ((self->flags & (ATTR_FLAG_POLICY_SET | ATTR_FLAG_SCHED_SET))
      == (ATTR_FLAG_POLICY_SET | ATTR_FLAG_SCHED_SET))
    return self->schedparam.sched_priority;

  int result = 0;

  /* See CREATE THREAD NOTES in nptl/pthread_create.c.  */
  lll_lock (self->lock, LLL_PRIVATE);

  if ((self->flags & ATTR_FLAG_SCHED_SET) == 0)
    {
      if (__sched_getparam (self->tid, &self->schedparam) != 0)
	result = -1;
      else
	self->flags |= ATTR_FLAG_SCHED_SET;
    }

  if ((self->flags & ATTR_FLAG_POLICY_SET) == 0)
    {
      self->schedpolicy = __sched_getscheduler (self->tid);
      if (self->schedpolicy == -1)
	result = -1;
      else
	self->flags |= ATTR_FLAG_POLICY_SET;
    }

  if (result != -1)
    result = self->schedparam.sched_priority;

  lll_unlock (self->lock, LLL_PRIVATE);

  return result;
}