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merge(3p/absl): subtree merge of Abseil up to e19260f

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... notably, this includes Abseil's own StatusOr type, which
conflicted with our implementation (that was taken from TensorFlow).

Change-Id: Ie7d6764b64055caaeb8dc7b6b9d066291e6b538f
This commit is contained in:
Vincent Ambo 2020-11-21 14:43:54 +01:00
parent cc27324d02
commit 082c006c04
854 changed files with 11260 additions and 5296 deletions
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66
third_party/abseil_cpp/absl/synchronization/internal/waiter.cc vendored
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@ -48,6 +48,7 @@
#include "absl/base/optimization.h"
#include "absl/synchronization/internal/kernel_timeout.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace synchronization_internal {
@ -66,71 +67,6 @@ static void MaybeBecomeIdle() {
#if ABSL_WAITER_MODE == ABSL_WAITER_MODE_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_WAIT_BITSET
#define FUTEX_WAIT_BITSET 9
#endif
#ifndef FUTEX_PRIVATE_FLAG
#define FUTEX_PRIVATE_FLAG 128
#endif
#ifndef FUTEX_CLOCK_REALTIME
#define FUTEX_CLOCK_REALTIME 256
#endif
#ifndef FUTEX_BITSET_MATCH_ANY
#define FUTEX_BITSET_MATCH_ANY 0xFFFFFFFF
#endif
#endif
#if defined(__NR_futex_time64) && !defined(SYS_futex_time64)
#define SYS_futex_time64 __NR_futex_time64
#endif
#if defined(SYS_futex_time64) && !defined(SYS_futex)
#define SYS_futex SYS_futex_time64
#endif
class Futex {
public:
static int WaitUntil(std::atomic<int32_t> *v, int32_t val,
KernelTimeout t) {
int err = 0;
if (t.has_timeout()) {
// https://locklessinc.com/articles/futex_cheat_sheet/
// Unlike FUTEX_WAIT, FUTEX_WAIT_BITSET uses absolute time.
struct timespec abs_timeout = t.MakeAbsTimespec();
// Atomically check that the futex value is still 0, and if it
// is, sleep until abs_timeout or until woken by FUTEX_WAKE.
err = syscall(
SYS_futex, reinterpret_cast<int32_t *>(v),
FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME, val,
&abs_timeout, nullptr, FUTEX_BITSET_MATCH_ANY);
} else {
// Atomically check that the futex value is still 0, and if it
// is, sleep until woken by FUTEX_WAKE.
err = syscall(SYS_futex, reinterpret_cast<int32_t *>(v),
FUTEX_WAIT | FUTEX_PRIVATE_FLAG, val, nullptr);
}
if (err != 0) {
err = -errno;
}
return err;
}
static int Wake(std::atomic<int32_t> *v, int32_t count) {
int err = syscall(SYS_futex, reinterpret_cast<int32_t *>(v),
FUTEX_WAKE | FUTEX_PRIVATE_FLAG, count);
if (ABSL_PREDICT_FALSE(err < 0)) {
err = -errno;
}
return err;
}
};
Waiter::Waiter() {
futex_.store(0, std::memory_order_relaxed);
}