5e19b185fd
FUTEX_LOCK_PI uses CLOCK_REALTIME so adjust clock timebase accordingly. FUTEX_WAIT_BITSET, FUTEX_WAIT_REQUEUE_PI, FUTEX_LOCK_PI2 are updated to check the presence of FUTEX_CLOCK_REALTIME flag. Test: atest bionic-unit-tests Bug: 312787238 Bug: 315897315 Change-Id: I2d93286cf22d3b3d9f3757d49b46f7ee9ea5490c
97 lines
4.1 KiB
C++
97 lines
4.1 KiB
C++
/*
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* Copyright (C) 2017 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include "private/bionic_futex.h"
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#include <stdatomic.h>
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#include <time.h>
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#include "private/bionic_time_conversions.h"
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static inline __always_inline int FutexWithTimeout(volatile void* ftx, int op, int value,
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bool use_realtime_clock,
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const timespec* abs_timeout, int bitset) {
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// pthread's and semaphore's default behavior is to use CLOCK_REALTIME, however this behavior is
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// essentially never intended, as that clock is prone to change discontinuously.
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//
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// What users really intend is to use CLOCK_MONOTONIC, however only pthread_cond_timedwait()
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// provides this as an option and even there, a large amount of existing code does not opt into
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// CLOCK_MONOTONIC.
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//
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// We have seen numerous bugs directly attributable to this difference. Therefore, we provide
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// this general workaround to always use CLOCK_MONOTONIC for waiting, regardless of what the input
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// timespec is.
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timespec converted_timeout;
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if (abs_timeout) {
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if ((op & FUTEX_CMD_MASK) == FUTEX_LOCK_PI) {
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if (!use_realtime_clock) {
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realtime_time_from_monotonic_time(converted_timeout, *abs_timeout);
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abs_timeout = &converted_timeout;
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}
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} else {
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op &= ~FUTEX_CLOCK_REALTIME;
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if (use_realtime_clock) {
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monotonic_time_from_realtime_time(converted_timeout, *abs_timeout);
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abs_timeout = &converted_timeout;
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}
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}
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if (abs_timeout->tv_sec < 0) {
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return -ETIMEDOUT;
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}
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}
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return __futex(ftx, op, value, abs_timeout, bitset);
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}
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int __futex_wait_ex(volatile void* ftx, bool shared, int value, bool use_realtime_clock,
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const timespec* abs_timeout) {
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return FutexWithTimeout(ftx, (shared ? FUTEX_WAIT_BITSET : FUTEX_WAIT_BITSET_PRIVATE), value,
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use_realtime_clock, abs_timeout, FUTEX_BITSET_MATCH_ANY);
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}
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int __futex_pi_lock_ex(volatile void* ftx, bool shared, bool use_realtime_clock,
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const timespec* abs_timeout) {
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// We really want FUTEX_LOCK_PI2 which is default CLOCK_MONOTONIC, but that isn't supported
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// on linux before 5.14. FUTEX_LOCK_PI uses CLOCK_REALTIME. Here we verify support.
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static atomic_int lock_op = 0;
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int op = atomic_load_explicit(&lock_op, memory_order_relaxed);
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if (op == 0) {
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uint32_t tmp = 0;
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if (__futex(&tmp, FUTEX_LOCK_PI2, 0, nullptr, 0) == 0) {
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__futex(&tmp, FUTEX_UNLOCK_PI, 0, nullptr, 0);
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op = FUTEX_LOCK_PI2;
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} else {
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op = FUTEX_LOCK_PI;
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}
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atomic_store_explicit(&lock_op, op, memory_order_relaxed);
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}
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if (!shared) op |= FUTEX_PRIVATE_FLAG;
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return FutexWithTimeout(ftx, op, 0 /* value */, use_realtime_clock, abs_timeout, 0 /* bitset */);
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}
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