// 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

//

//      https://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.

#include "absl/base/internal/thread_identity.h"

#include <atomic>

#include <cassert>

#include <memory>

#include "absl/base/attributes.h"

#include "absl/base/call_once.h"

#include "absl/base/config.h"

#include "absl/base/internal/raw_logging.h"

#include "absl/base/internal/spinlock.h"

#if ABSL_THREAD_IDENTITY_MODE != ABSL_THREAD_IDENTITY_MODE_USE_CPP11

#include <pthread.h>

#ifndef __wasi__

// WASI does not provide this header, either way we disable use

// of signals with it below.

#include <signal.h>

#endif

#endif

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace base_internal {

#if ABSL_THREAD_IDENTITY_MODE != ABSL_THREAD_IDENTITY_MODE_USE_CPP11

namespace {

// Used to co-ordinate one-time creation of our pthread_key

absl::once_flag init_thread_identity_key_once;

pthread_key_t thread_identity_pthread_key;

std::atomic<bool> pthread_key_initialized(false);

void AllocateThreadIdentityKey(ThreadIdentityReclaimerFunction reclaimer) {

  pthread_key_create(&thread_identity_pthread_key, reclaimer);

  pthread_key_initialized.store(true, std::memory_order_release);

}

}  // namespace

#endif

#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS || \

    ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11

// The actual TLS storage for a thread's currently associated ThreadIdentity.

// This is referenced by inline accessors in the header.

// "protected" visibility ensures that if multiple instances of Abseil code

// exist within a process (via dlopen() or similar), references to

// thread_identity_ptr from each instance of the code will refer to

// *different* instances of this ptr.

// Apple platforms have the visibility attribute, but issue a compile warning

// that protected visibility is unsupported.

ABSL_CONST_INIT  // Must come before __attribute__((visibility("protected")))

#if ABSL_HAVE_ATTRIBUTE(visibility) && !defined(__APPLE__)

    __attribute__((visibility("protected")))

#endif  // ABSL_HAVE_ATTRIBUTE(visibility) && !defined(__APPLE__)

#if ABSL_PER_THREAD_TLS

    // Prefer __thread to thread_local as benchmarks indicate it is a bit

    // faster.

    ABSL_PER_THREAD_TLS_KEYWORD ThreadIdentity* thread_identity_ptr = nullptr;

#elif defined(ABSL_HAVE_THREAD_LOCAL)

    thread_local ThreadIdentity* thread_identity_ptr = nullptr;

#endif  // ABSL_PER_THREAD_TLS

#endif  // TLS or CPP11

void SetCurrentThreadIdentity(ThreadIdentity* identity,

                              ThreadIdentityReclaimerFunction reclaimer) {

  assert(CurrentThreadIdentityIfPresent() == nullptr);

  // Associate our destructor.

  // NOTE: This call to pthread_setspecific is currently the only immovable

  // barrier to CurrentThreadIdentity() always being async signal safe.

#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC

  // NOTE: Not async-safe.  But can be open-coded.

  absl::call_once(init_thread_identity_key_once, AllocateThreadIdentityKey,

                  reclaimer);

#if defined(__wasi__) || defined(__EMSCRIPTEN__) || defined(__MINGW32__) || \

    defined(__hexagon__)

  // Emscripten, WASI and MinGW pthread implementations do not support

  // signals. See

  // https://kripken.github.io/emscripten-site/docs/porting/pthreads.html for

  // more information.

  pthread_setspecific(thread_identity_pthread_key,

                      reinterpret_cast<void*>(identity));

#else

  // We must mask signals around the call to setspecific as with current glibc,

  // a concurrent getspecific (needed for GetCurrentThreadIdentityIfPresent())

  // may zero our value.

  //

  // While not officially async-signal safe, getspecific within a signal handler

  // is otherwise OK.

  sigset_t all_signals;

  sigset_t curr_signals;

  sigfillset(&all_signals);

  pthread_sigmask(SIG_SETMASK, &all_signals, &curr_signals);

  pthread_setspecific(thread_identity_pthread_key,

                      reinterpret_cast<void*>(identity));

  pthread_sigmask(SIG_SETMASK, &curr_signals, nullptr);

#endif  // !__EMSCRIPTEN__ && !__MINGW32__

#elif ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS

  // NOTE: Not async-safe.  But can be open-coded.

  absl::call_once(init_thread_identity_key_once, AllocateThreadIdentityKey,

                  reclaimer);

  pthread_setspecific(thread_identity_pthread_key,

                      reinterpret_cast<void*>(identity));

  thread_identity_ptr = identity;

#elif ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11

  thread_local std::unique_ptr<ThreadIdentity, ThreadIdentityReclaimerFunction>

      holder(identity, reclaimer);

  thread_identity_ptr = identity;

#else

#error Unimplemented ABSL_THREAD_IDENTITY_MODE

#endif

}

#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS || \

    ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11

// Please see the comment on `CurrentThreadIdentityIfPresent` in

// thread_identity.h. When we cannot expose thread_local variables in

// headers, we opt for the correct-but-slower option of not inlining this

// function.

#ifndef ABSL_INTERNAL_INLINE_CURRENT_THREAD_IDENTITY_IF_PRESENT

ThreadIdentity* CurrentThreadIdentityIfPresent() { return thread_identity_ptr; }

#endif

#endif

void ClearCurrentThreadIdentity() {

#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS || \

    ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11

  thread_identity_ptr = nullptr;

#elif ABSL_THREAD_IDENTITY_MODE == \

    ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC

  // pthread_setspecific expected to clear value on destruction

  assert(CurrentThreadIdentityIfPresent() == nullptr);

#endif

}

#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC

ThreadIdentity* CurrentThreadIdentityIfPresent() {

  bool initialized = pthread_key_initialized.load(std::memory_order_acquire);

  if (!initialized) {

    return nullptr;

  }

  return reinterpret_cast<ThreadIdentity*>(

      pthread_getspecific(thread_identity_pthread_key));

}

#endif

}  // namespace base_internal

ABSL_NAMESPACE_END

}  // namespace absl