summaryrefslogtreecommitdiff
path: root/nptl/pthread_cond_timedwait.c
blob: 10b0a61a2a680ed86cbacf5d132fe7759ee9f042 (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
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
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
/* Copyright (C) 2003-2015 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.

   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 <endian.h>
#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <pthread.h>
#include <pthreadP.h>
#include <sys/time.h>
#include <kernel-features.h>

#include <shlib-compat.h>

#ifndef HAVE_CLOCK_GETTIME_VSYSCALL
# undef INTERNAL_VSYSCALL
# define INTERNAL_VSYSCALL INTERNAL_SYSCALL
# undef INLINE_VSYSCALL
# define INLINE_VSYSCALL INLINE_SYSCALL
#else
# include <libc-vdso.h>
#endif

/* Cleanup handler, defined in pthread_cond_wait.c.  */
extern void __condvar_cleanup (void *arg)
     __attribute__ ((visibility ("hidden")));

struct _condvar_cleanup_buffer
{
  int oldtype;
  pthread_cond_t *cond;
  pthread_mutex_t *mutex;
  unsigned int bc_seq;
};

int
__pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
			  const struct timespec *abstime)
{
  struct _pthread_cleanup_buffer buffer;
  struct _condvar_cleanup_buffer cbuffer;
  int result = 0;

  /* Catch invalid parameters.  */
  if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
    return EINVAL;

  int pshared = (cond->__data.__mutex == (void *) ~0l)
		? LLL_SHARED : LLL_PRIVATE;

#if (defined lll_futex_timed_wait_requeue_pi \
     && defined __ASSUME_REQUEUE_PI)
  int pi_flag = 0;
#endif

  /* Make sure we are alone.  */
  lll_lock (cond->__data.__lock, pshared);

  /* Now we can release the mutex.  */
  int err = __pthread_mutex_unlock_usercnt (mutex, 0);
  if (err)
    {
      lll_unlock (cond->__data.__lock, pshared);
      return err;
    }

  /* We have one new user of the condvar.  */
  ++cond->__data.__total_seq;
  ++cond->__data.__futex;
  cond->__data.__nwaiters += 1 << COND_NWAITERS_SHIFT;

  /* Work around the fact that the kernel rejects negative timeout values
     despite them being valid.  */
  if (__glibc_unlikely (abstime->tv_sec < 0))
    goto timeout;

  /* Remember the mutex we are using here.  If there is already a
     different address store this is a bad user bug.  Do not store
     anything for pshared condvars.  */
  if (cond->__data.__mutex != (void *) ~0l)
    cond->__data.__mutex = mutex;

  /* Prepare structure passed to cancellation handler.  */
  cbuffer.cond = cond;
  cbuffer.mutex = mutex;

  /* Before we block we enable cancellation.  Therefore we have to
     install a cancellation handler.  */
  __pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer);

  /* The current values of the wakeup counter.  The "woken" counter
     must exceed this value.  */
  unsigned long long int val;
  unsigned long long int seq;
  val = seq = cond->__data.__wakeup_seq;
  /* Remember the broadcast counter.  */
  cbuffer.bc_seq = cond->__data.__broadcast_seq;

  while (1)
    {
#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
     || !defined lll_futex_timed_wait_bitset)
      struct timespec rt;
      {
# ifdef __NR_clock_gettime
	INTERNAL_SYSCALL_DECL (err);
	(void) INTERNAL_VSYSCALL (clock_gettime, err, 2,
				  (cond->__data.__nwaiters
				   & ((1 << COND_NWAITERS_SHIFT) - 1)),
				  &rt);
	/* Convert the absolute timeout value to a relative timeout.  */
	rt.tv_sec = abstime->tv_sec - rt.tv_sec;
	rt.tv_nsec = abstime->tv_nsec - rt.tv_nsec;
# else
	/* Get the current time.  So far we support only one clock.  */
	struct timeval tv;
	(void) __gettimeofday (&tv, NULL);

	/* Convert the absolute timeout value to a relative timeout.  */
	rt.tv_sec = abstime->tv_sec - tv.tv_sec;
	rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
# endif
      }
      if (rt.tv_nsec < 0)
	{
	  rt.tv_nsec += 1000000000;
	  --rt.tv_sec;
	}
      /* Did we already time out?  */
      if (__glibc_unlikely (rt.tv_sec < 0))
	{
	  if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
	    goto bc_out;

	  goto timeout;
	}
#endif

      unsigned int futex_val = cond->__data.__futex;

      /* Prepare to wait.  Release the condvar futex.  */
      lll_unlock (cond->__data.__lock, pshared);

      /* Enable asynchronous cancellation.  Required by the standard.  */
      cbuffer.oldtype = __pthread_enable_asynccancel ();

/* REQUEUE_PI was implemented after FUTEX_CLOCK_REALTIME, so it is sufficient
   to check just the former.  */
#if (defined lll_futex_timed_wait_requeue_pi \
     && defined __ASSUME_REQUEUE_PI)
      /* If pi_flag remained 1 then it means that we had the lock and the mutex
	 but a spurious waker raced ahead of us.  Give back the mutex before
	 going into wait again.  */
      if (pi_flag)
	{
	  __pthread_mutex_cond_lock_adjust (mutex);
	  __pthread_mutex_unlock_usercnt (mutex, 0);
	}
      pi_flag = USE_REQUEUE_PI (mutex);

      if (pi_flag)
	{
	  unsigned int clockbit = (cond->__data.__nwaiters & 1
				   ? 0 : FUTEX_CLOCK_REALTIME);
	  err = lll_futex_timed_wait_requeue_pi (&cond->__data.__futex,
						 futex_val, abstime, clockbit,
						 &mutex->__data.__lock,
						 pshared);
	  pi_flag = (err == 0);
	}
      else
#endif

	{
#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
     || !defined lll_futex_timed_wait_bitset)
	  /* Wait until woken by signal or broadcast.  */
	  err = lll_futex_timed_wait (&cond->__data.__futex,
				      futex_val, &rt, pshared);
#else
	  unsigned int clockbit = (cond->__data.__nwaiters & 1
				   ? 0 : FUTEX_CLOCK_REALTIME);
	  err = lll_futex_timed_wait_bitset (&cond->__data.__futex, futex_val,
					     abstime, clockbit, pshared);
#endif
	}

      /* Disable asynchronous cancellation.  */
      __pthread_disable_asynccancel (cbuffer.oldtype);

      /* We are going to look at shared data again, so get the lock.  */
      lll_lock (cond->__data.__lock, pshared);

      /* If a broadcast happened, we are done.  */
      if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
	goto bc_out;

      /* Check whether we are eligible for wakeup.  */
      val = cond->__data.__wakeup_seq;
      if (val != seq && cond->__data.__woken_seq != val)
	break;

      /* Not woken yet.  Maybe the time expired?  */
      if (__glibc_unlikely (err == -ETIMEDOUT))
	{
	timeout:
	  /* Yep.  Adjust the counters.  */
	  ++cond->__data.__wakeup_seq;
	  ++cond->__data.__futex;

	  /* The error value.  */
	  result = ETIMEDOUT;
	  break;
	}
    }

  /* Another thread woken up.  */
  ++cond->__data.__woken_seq;

 bc_out:

  cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;

  /* If pthread_cond_destroy was called on this variable already,
     notify the pthread_cond_destroy caller all waiters have left
     and it can be successfully destroyed.  */
  if (cond->__data.__total_seq == -1ULL
      && cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
    lll_futex_wake (&cond->__data.__nwaiters, 1, pshared);

  /* We are done with the condvar.  */
  lll_unlock (cond->__data.__lock, pshared);

  /* The cancellation handling is back to normal, remove the handler.  */
  __pthread_cleanup_pop (&buffer, 0);

  /* Get the mutex before returning.  */
#if (defined lll_futex_timed_wait_requeue_pi \
     && defined __ASSUME_REQUEUE_PI)
  if (pi_flag)
    {
      __pthread_mutex_cond_lock_adjust (mutex);
      err = 0;
    }
  else
#endif
    err = __pthread_mutex_cond_lock (mutex);

  return err ?: result;
}

versioned_symbol (libpthread, __pthread_cond_timedwait, pthread_cond_timedwait,
		  GLIBC_2_3_2);