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/*
* Copyright (C) 2017 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "private/bionic_futex.h"
#include <time.h>
#include "private/bionic_time_conversions.h"
static inline __always_inline int FutexWithTimeout(volatile void* ftx, int op, int value,
bool use_realtime_clock,
const timespec* abs_timeout, int bitset) {
const timespec* futex_abs_timeout = abs_timeout;
// pthread's and semaphore's default behavior is to use CLOCK_REALTIME, however this behavior is
// essentially never intended, as that clock is prone to change discontinuously.
//
// What users really intend is to use CLOCK_MONOTONIC, however only pthread_cond_timedwait()
// provides this as an option and even there, a large amount of existing code does not opt into
// CLOCK_MONOTONIC.
//
// We have seen numerous bugs directly attributable to this difference. Therefore, we provide
// this general workaround to always use CLOCK_MONOTONIC for waiting, regardless of what the input
// timespec is.
timespec converted_monotonic_abs_timeout;
if (abs_timeout && use_realtime_clock) {
monotonic_time_from_realtime_time(converted_monotonic_abs_timeout, *abs_timeout);
if (converted_monotonic_abs_timeout.tv_sec < 0) {
return -ETIMEDOUT;
}
futex_abs_timeout = &converted_monotonic_abs_timeout;
}
return __futex(ftx, op, value, futex_abs_timeout, bitset);
}
int __futex_wait_ex(volatile void* ftx, bool shared, int value, bool use_realtime_clock,
const timespec* abs_timeout) {
return FutexWithTimeout(ftx, (shared ? FUTEX_WAIT_BITSET : FUTEX_WAIT_BITSET_PRIVATE), value,
use_realtime_clock, abs_timeout, FUTEX_BITSET_MATCH_ANY);
}
int __futex_pi_lock_ex(volatile void* ftx, bool shared, bool use_realtime_clock,
const timespec* abs_timeout) {
return FutexWithTimeout(ftx, (shared ? FUTEX_LOCK_PI : FUTEX_LOCK_PI_PRIVATE), 0,
use_realtime_clock, abs_timeout, 0);
}
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