1 /*
2 * Copyright (C) 2017 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include "private/bionic_futex.h"
30
31 #include <time.h>
32
33 #include "private/bionic_time_conversions.h"
34
FutexWithTimeout(volatile void * ftx,int op,int value,bool use_realtime_clock,const timespec * abs_timeout,int bitset)35 static inline __always_inline int FutexWithTimeout(volatile void* ftx, int op, int value,
36 bool use_realtime_clock,
37 const timespec* abs_timeout, int bitset) {
38 const timespec* futex_abs_timeout = abs_timeout;
39 // pthread's and semaphore's default behavior is to use CLOCK_REALTIME, however this behavior is
40 // essentially never intended, as that clock is prone to change discontinuously.
41 //
42 // What users really intend is to use CLOCK_MONOTONIC, however only pthread_cond_timedwait()
43 // provides this as an option and even there, a large amount of existing code does not opt into
44 // CLOCK_MONOTONIC.
45 //
46 // We have seen numerous bugs directly attributable to this difference. Therefore, we provide
47 // this general workaround to always use CLOCK_MONOTONIC for waiting, regardless of what the input
48 // timespec is.
49 timespec converted_monotonic_abs_timeout;
50 if (abs_timeout && use_realtime_clock) {
51 monotonic_time_from_realtime_time(converted_monotonic_abs_timeout, *abs_timeout);
52 if (converted_monotonic_abs_timeout.tv_sec < 0) {
53 return -ETIMEDOUT;
54 }
55 futex_abs_timeout = &converted_monotonic_abs_timeout;
56 }
57
58 return __futex(ftx, op, value, futex_abs_timeout, bitset);
59 }
60
__futex_wait_ex(volatile void * ftx,bool shared,int value,bool use_realtime_clock,const timespec * abs_timeout)61 int __futex_wait_ex(volatile void* ftx, bool shared, int value, bool use_realtime_clock,
62 const timespec* abs_timeout) {
63 return FutexWithTimeout(ftx, (shared ? FUTEX_WAIT_BITSET : FUTEX_WAIT_BITSET_PRIVATE), value,
64 use_realtime_clock, abs_timeout, FUTEX_BITSET_MATCH_ANY);
65 }
66
__futex_pi_lock_ex(volatile void * ftx,bool shared,bool use_realtime_clock,const timespec * abs_timeout)67 int __futex_pi_lock_ex(volatile void* ftx, bool shared, bool use_realtime_clock,
68 const timespec* abs_timeout) {
69 return FutexWithTimeout(ftx, (shared ? FUTEX_LOCK_PI : FUTEX_LOCK_PI_PRIVATE), 0,
70 use_realtime_clock, abs_timeout, 0);
71 }
72