Export of internal Abseil changes.

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c508ee8bcc38dad1019c0ad744c47ac70efd36b7 by Derek Mauro <dmauro@google.com>:

Opensource the Linux specific SpinLock Wait/Wake implementation.

PiperOrigin-RevId: 209420888

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c13113e19973d496f3e798c0e6d5569c78e41466 by Derek Mauro <dmauro@google.com>:

Fix build error from https://github.com/abseil/abseil-cpp/issues/159

PiperOrigin-RevId: 209152118
GitOrigin-RevId: c508ee8bcc38dad1019c0ad744c47ac70efd36b7
Change-Id: I1a287df973198f9e26936d8f91031bb354db0c71
This commit is contained in:
Abseil Team 2018-08-20 08:18:32 -07:00 committed by Derek Mauro
parent ad5c960b2e
commit d8cfe9f2a7
5 changed files with 80 additions and 3 deletions

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@ -30,6 +30,7 @@ cc_library(
name = "spinlock_wait",
srcs = [
"internal/spinlock_akaros.inc",
"internal/spinlock_linux.inc",
"internal/spinlock_posix.inc",
"internal/spinlock_wait.cc",
"internal/spinlock_win32.inc",

View file

@ -0,0 +1,72 @@
// Copyright 2018 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// This file is a Linux-specific part of spinlock_wait.cc
#include <linux/futex.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <atomic>
#include <cerrno>
#include <climits>
#include <cstdint>
#include <ctime>
#include "absl/base/attributes.h"
// The SpinLock lockword is `std::atomic<uint32_t>`. Here we assert that
// `std::atomic<uint32_t>` is bitwise equivalent of the `int` expected
// by SYS_futex. We also assume that reads/writes done to the lockword
// by SYS_futex have rational semantics with regard to the
// std::atomic<> API. C++ provides no guarantees of these assumptions,
// but they are believed to hold in practice.
static_assert(sizeof(std::atomic<uint32_t>) == sizeof(int),
"SpinLock lockword has the wrong size for a futex");
// Some Android headers are missing these definitions even though they
// support these futex operations.
#ifdef __BIONIC__
#ifndef SYS_futex
#define SYS_futex __NR_futex
#endif
#ifndef FUTEX_PRIVATE_FLAG
#define FUTEX_PRIVATE_FLAG 128
#endif
#endif
extern "C" {
ABSL_ATTRIBUTE_WEAK void AbslInternalSpinLockDelay(
std::atomic<uint32_t> *w, uint32_t value, int loop,
absl::base_internal::SchedulingMode) {
if (loop != 0) {
int save_errno = errno;
struct timespec tm;
tm.tv_sec = 0;
// Increase the delay; we expect (but do not rely on) explicit wakeups.
// We don't rely on explicit wakeups because we intentionally allow for
// a race on the kSpinLockSleeper bit.
tm.tv_nsec = 16 * absl::base_internal::SpinLockSuggestedDelayNS(loop);
syscall(SYS_futex, w, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, value, &tm);
errno = save_errno;
}
}
ABSL_ATTRIBUTE_WEAK void AbslInternalSpinLockWake(std::atomic<uint32_t> *w,
bool all) {
syscall(SYS_futex, w, FUTEX_WAKE | FUTEX_PRIVATE_FLAG, all ? INT_MAX : 1, 0);
}
} // extern "C"

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@ -13,7 +13,7 @@
// limitations under the License.
// The OS-specific header included below must provide two calls:
// base::subtle::SpinLockDelay() and base::subtle::SpinLockWake().
// AbslInternalSpinLockDelay() and AbslInternalSpinLockWake().
// See spinlock_wait.h for the specs.
#include <atomic>
@ -23,6 +23,8 @@
#if defined(_WIN32)
#include "absl/base/internal/spinlock_win32.inc"
#elif defined(__linux__)
#include "absl/base/internal/spinlock_linux.inc"
#elif defined(__akaros__)
#include "absl/base/internal/spinlock_akaros.inc"
#else

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@ -28,7 +28,8 @@
#define ABSL_EXPECT_DEBUG_DEATH(statement, regex) \
EXPECT_DEBUG_DEATH(statement, ".*")
#else
#define ABSL_EXPECT_DEBUG_DEATH EXPECT_DEBUG_DEATH
#define ABSL_EXPECT_DEBUG_DEATH(statement, regex) \
EXPECT_DEBUG_DEATH(statement, regex)
#endif
namespace {

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@ -35,7 +35,8 @@
#define ABSL_EXPECT_DEATH_IF_SUPPORTED(statement, regex) \
EXPECT_DEATH_IF_SUPPORTED(statement, ".*")
#else
#define ABSL_EXPECT_DEATH_IF_SUPPORTED EXPECT_DEATH_IF_SUPPORTED
#define ABSL_EXPECT_DEATH_IF_SUPPORTED(statement, regex) \
EXPECT_DEATH_IF_SUPPORTED(statement, regex)
#endif
namespace {