Changes imported from Abseil "staging" branch:

- fbff677ef850865ea67ed6771a8ed348be181e8e Modify sysinfo.cc to support GetTID on Akaros. by Abseil Team <absl-team@google.com>
  - f1c2929e08a3d4181e08cb5014c4a569306fd922 Two functions that did not refer to their arguments unles... by Abseil Team <absl-team@google.com>
  - ee43cc3bfdb4d84d40eee31fb25ecdc1aa060f47 Support Akaros (https://akaros.org) in the ABSL spinlock_... by Abseil Team <absl-team@google.com>
  - 6869c8c5253126459d6c7f0aa708d8612c8e5963 Make sure vdso_base_ is constant-intialized. by Abseil Team <absl-team@google.com>
  - d54e0366efc8d44cd5da5fd157734da966dc45e8 Add missing include for assert used by ABSL_ASSERT. by Derek Mauro <dmauro@google.com>
  - a5139775f3917bb5201e7fc838135766daa05b8d When building against GLIBC-2.16 or newer, use getauxval(... by Abseil Team <absl-team@google.com>

GitOrigin-RevId: fbff677ef850865ea67ed6771a8ed348be181e8e
Change-Id: Ie3549f6ef054783dd104304d2faf8d9800c16b83
This commit is contained in:
Abseil Team 2017-10-24 10:37:49 -07:00 committed by Jon Cohen
parent 5fcbe86e7b
commit dedb4eec6c
9 changed files with 120 additions and 34 deletions

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@ -28,6 +28,7 @@ licenses(["notice"]) # Apache 2.0
cc_library(
name = "spinlock_wait",
srcs = [
"internal/spinlock_akaros.inc",
"internal/spinlock_posix.inc",
"internal/spinlock_wait.cc",
"internal/spinlock_win32.inc",

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@ -0,0 +1,35 @@
// Copyright 2017 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 an Akaros-specific part of spinlock_wait.cc
#include <atomic>
#include "absl/base/internal/scheduling_mode.h"
extern "C" {
ABSL_ATTRIBUTE_WEAK void AbslInternalSpinLockDelay(
std::atomic<uint32_t>* /* lock_word */, uint32_t /* value */,
int /* loop */, absl::base_internal::SchedulingMode /* mode */) {
// In Akaros, one must take care not to call anything that could cause a
// malloc(), a blocking system call, or a uthread_yield() while holding a
// spinlock. Our callers assume will not call into libraries or other
// arbitrary code.
}
ABSL_ATTRIBUTE_WEAK void AbslInternalSpinLockWake(
std::atomic<uint32_t>* /* lock_word */, bool /* all */) {}
} // extern "C"

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@ -23,6 +23,8 @@
#if defined(_WIN32)
#include "absl/base/internal/spinlock_win32.inc"
#elif defined(__akaros__)
#include "absl/base/internal/spinlock_akaros.inc"
#else
#include "absl/base/internal/spinlock_posix.inc"
#endif

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@ -284,6 +284,30 @@ pid_t GetTID() {
return syscall(SYS_gettid);
}
#elif defined(__akaros__)
pid_t GetTID() {
// Akaros has a concept of "vcore context", which is the state the program
// is forced into when we need to make a user-level scheduling decision, or
// run a signal handler. This is analogous to the interrupt context that a
// CPU might enter if it encounters some kind of exception.
//
// There is no current thread context in vcore context, but we need to give
// a reasonable answer if asked for a thread ID (e.g., in a signal handler).
// Thread 0 always exists, so if we are in vcore context, we return that.
//
// Otherwise, we know (since we are using pthreads) that the uthread struct
// current_uthread is pointing to is the first element of a
// struct pthread_tcb, so we extract and return the thread ID from that.
//
// TODO(dcross): Akaros anticipates moving the thread ID to the uthread
// structure at some point. We should modify this code to remove the cast
// when that happens.
if (in_vcore_context())
return 0;
return reinterpret_cast<struct pthread_tcb *>(current_uthread)->id;
}
#else
// Fallback implementation of GetTID using pthread_getspecific.

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@ -29,6 +29,7 @@
#ifndef ABSL_BASE_MACROS_H_
#define ABSL_BASE_MACROS_H_
#include <cassert>
#include <cstddef>
#include "absl/base/port.h"

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@ -75,8 +75,9 @@ const T *GetTableElement(const ElfW(Ehdr) * ehdr, ElfW(Off) table_offset,
} // namespace
const void *const ElfMemImage::kInvalidBase =
reinterpret_cast<const void *>(~0L);
// The value of this variable doesn't matter; it's used only for its
// unique address.
const int ElfMemImage::kInvalidBaseSentinel = 0;
ElfMemImage::ElfMemImage(const void *base) {
ABSL_RAW_CHECK(base != kInvalidBase, "bad pointer");

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@ -43,9 +43,14 @@ namespace debug_internal {
// An in-memory ELF image (may not exist on disk).
class ElfMemImage {
private:
// Sentinel: there could never be an elf image at &kInvalidBaseSentinel.
static const int kInvalidBaseSentinel;
public:
// Sentinel: there could never be an elf image at this address.
static const void *const kInvalidBase;
static constexpr const void *const kInvalidBase =
static_cast<const void*>(&kInvalidBaseSentinel);
// Information about a single vdso symbol.
// All pointers are into .dynsym, .dynstr, or .text of the VDSO.

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@ -114,7 +114,9 @@ static const int kMaxFrameBytes = 100000;
// vuc is a ucontext_t *. We use void* to avoid the use
// of ucontext_t on non-POSIX systems.
static uintptr_t GetFP(const void *vuc) {
#if defined(__linux__)
#if !defined(__linux__)
static_cast<void>(vuc); // Avoid an unused argument compiler warning.
#else
if (vuc != nullptr) {
auto *uc = reinterpret_cast<const ucontext_t *>(vuc);
#if defined(__i386__)

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@ -20,10 +20,15 @@
#ifdef ABSL_HAVE_VDSO_SUPPORT // defined in vdso_support.h
#include <errno.h>
#include <fcntl.h>
#include <sys/syscall.h>
#include <unistd.h>
#if __GLIBC_PREREQ(2, 16) // GLIBC-2.16 implements getauxval.
#include <sys/auxv.h>
#endif
#include "absl/base/dynamic_annotations.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/base/port.h"
@ -35,8 +40,10 @@
namespace absl {
namespace debug_internal {
ABSL_CONST_INIT
std::atomic<const void *> VDSOSupport::vdso_base_(
debug_internal::ElfMemImage::kInvalidBase);
std::atomic<VDSOSupport::GetCpuFn> VDSOSupport::getcpu_fn_(&InitAndGetCPU);
VDSOSupport::VDSOSupport()
// If vdso_base_ is still set to kInvalidBase, we got here
@ -56,37 +63,44 @@ VDSOSupport::VDSOSupport()
// Finally, even if there is a race here, it is harmless, because
// the operation should be idempotent.
const void *VDSOSupport::Init() {
if (vdso_base_.load(std::memory_order_relaxed) ==
debug_internal::ElfMemImage::kInvalidBase) {
{
// Valgrind zaps AT_SYSINFO_EHDR and friends from the auxv[]
// on stack, and so glibc works as if VDSO was not present.
// But going directly to kernel via /proc/self/auxv below bypasses
// Valgrind zapping. So we check for Valgrind separately.
if (RunningOnValgrind()) {
vdso_base_.store(nullptr, std::memory_order_relaxed);
getcpu_fn_.store(&GetCPUViaSyscall, std::memory_order_relaxed);
return nullptr;
}
int fd = open("/proc/self/auxv", O_RDONLY);
if (fd == -1) {
// Kernel too old to have a VDSO.
vdso_base_.store(nullptr, std::memory_order_relaxed);
getcpu_fn_.store(&GetCPUViaSyscall, std::memory_order_relaxed);
return nullptr;
}
ElfW(auxv_t) aux;
while (read(fd, &aux, sizeof(aux)) == sizeof(aux)) {
if (aux.a_type == AT_SYSINFO_EHDR) {
vdso_base_.store(reinterpret_cast<void *>(aux.a_un.a_val),
std::memory_order_relaxed);
break;
}
}
close(fd);
const auto kInvalidBase = debug_internal::ElfMemImage::kInvalidBase;
#if __GLIBC_PREREQ(2, 16)
if (vdso_base_.load(std::memory_order_relaxed) == kInvalidBase) {
errno = 0;
const void *const sysinfo_ehdr =
reinterpret_cast<const void *>(getauxval(AT_SYSINFO_EHDR));
if (errno == 0) {
vdso_base_.store(sysinfo_ehdr, std::memory_order_relaxed);
}
if (vdso_base_.load(std::memory_order_relaxed) ==
debug_internal::ElfMemImage::kInvalidBase) {
}
#endif // __GLIBC_PREREQ(2, 16)
if (vdso_base_.load(std::memory_order_relaxed) == kInvalidBase) {
// Valgrind zaps AT_SYSINFO_EHDR and friends from the auxv[]
// on stack, and so glibc works as if VDSO was not present.
// But going directly to kernel via /proc/self/auxv below bypasses
// Valgrind zapping. So we check for Valgrind separately.
if (RunningOnValgrind()) {
vdso_base_.store(nullptr, std::memory_order_relaxed);
getcpu_fn_.store(&GetCPUViaSyscall, std::memory_order_relaxed);
return nullptr;
}
int fd = open("/proc/self/auxv", O_RDONLY);
if (fd == -1) {
// Kernel too old to have a VDSO.
vdso_base_.store(nullptr, std::memory_order_relaxed);
getcpu_fn_.store(&GetCPUViaSyscall, std::memory_order_relaxed);
return nullptr;
}
ElfW(auxv_t) aux;
while (read(fd, &aux, sizeof(aux)) == sizeof(aux)) {
if (aux.a_type == AT_SYSINFO_EHDR) {
vdso_base_.store(reinterpret_cast<void *>(aux.a_un.a_val),
std::memory_order_relaxed);
break;
}
}
close(fd);
if (vdso_base_.load(std::memory_order_relaxed) == kInvalidBase) {
// Didn't find AT_SYSINFO_EHDR in auxv[].
vdso_base_.store(nullptr, std::memory_order_relaxed);
}
@ -135,6 +149,7 @@ long VDSOSupport::GetCPUViaSyscall(unsigned *cpu, // NOLINT(runtime/int)
return syscall(SYS_getcpu, cpu, nullptr, nullptr);
#else
// x86_64 never implemented sys_getcpu(), except as a VDSO call.
static_cast<void>(cpu); // Avoid an unused argument compiler warning.
errno = ENOSYS;
return -1;
#endif