|
|
|
// 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.
|
|
|
|
//
|
|
|
|
// Each active thread has an ThreadIdentity that may represent the thread in
|
|
|
|
// various level interfaces. ThreadIdentity objects are never deallocated.
|
|
|
|
// When a thread terminates, its ThreadIdentity object may be reused for a
|
|
|
|
// thread created later.
|
|
|
|
|
|
|
|
#ifndef ABSL_BASE_INTERNAL_THREAD_IDENTITY_H_
|
|
|
|
#define ABSL_BASE_INTERNAL_THREAD_IDENTITY_H_
|
|
|
|
|
|
|
|
#ifndef _WIN32
|
|
|
|
#include <pthread.h>
|
|
|
|
// Defines __GOOGLE_GRTE_VERSION__ (via glibc-specific features.h) when
|
|
|
|
// supported.
|
|
|
|
#include <unistd.h>
|
|
|
|
#endif
|
|
|
|
|
|
|
|
#include <atomic>
|
|
|
|
#include <cstdint>
|
|
|
|
|
|
|
|
#include "absl/base/config.h"
|
|
|
|
#include "absl/base/internal/per_thread_tls.h"
|
|
|
|
#include "absl/base/optimization.h"
|
|
|
|
|
|
|
|
namespace absl {
|
|
|
|
ABSL_NAMESPACE_BEGIN
|
|
|
|
|
|
|
|
struct SynchLocksHeld;
|
|
|
|
struct SynchWaitParams;
|
|
|
|
|
|
|
|
namespace base_internal {
|
|
|
|
|
|
|
|
class SpinLock;
|
|
|
|
struct ThreadIdentity;
|
|
|
|
|
|
|
|
// Used by the implementation of absl::Mutex and absl::CondVar.
|
|
|
|
struct PerThreadSynch {
|
|
|
|
// The internal representation of absl::Mutex and absl::CondVar rely
|
|
|
|
// on the alignment of PerThreadSynch. Both store the address of the
|
|
|
|
// PerThreadSynch in the high-order bits of their internal state,
|
|
|
|
// which means the low kLowZeroBits of the address of PerThreadSynch
|
|
|
|
// must be zero.
|
|
|
|
static constexpr int kLowZeroBits = 8;
|
|
|
|
static constexpr int kAlignment = 1 << kLowZeroBits;
|
|
|
|
|
|
|
|
// Returns the associated ThreadIdentity.
|
|
|
|
// This can be implemented as a cast because we guarantee
|
|
|
|
// PerThreadSynch is the first element of ThreadIdentity.
|
|
|
|
ThreadIdentity* thread_identity() {
|
|
|
|
return reinterpret_cast<ThreadIdentity*>(this);
|
|
|
|
}
|
|
|
|
|
|
|
|
PerThreadSynch *next; // Circular waiter queue; initialized to 0.
|
|
|
|
PerThreadSynch *skip; // If non-zero, all entries in Mutex queue
|
|
|
|
// up to and including "skip" have same
|
|
|
|
// condition as this, and will be woken later
|
|
|
|
bool may_skip; // if false while on mutex queue, a mutex unlocker
|
|
|
|
// is using this PerThreadSynch as a terminator. Its
|
|
|
|
// skip field must not be filled in because the loop
|
|
|
|
// might then skip over the terminator.
|
|
|
|
bool wake; // This thread is to be woken from a Mutex.
|
|
|
|
// If "x" is on a waiter list for a mutex, "x->cond_waiter" is true iff the
|
|
|
|
// waiter is waiting on the mutex as part of a CV Wait or Mutex Await.
|
|
|
|
//
|
|
|
|
// The value of "x->cond_waiter" is meaningless if "x" is not on a
|
|
|
|
// Mutex waiter list.
|
|
|
|
bool cond_waiter;
|
|
|
|
bool maybe_unlocking; // Valid at head of Mutex waiter queue;
|
|
|
|
// true if UnlockSlow could be searching
|
|
|
|
// for a waiter to wake. Used for an optimization
|
|
|
|
// in Enqueue(). true is always a valid value.
|
|
|
|
// Can be reset to false when the unlocker or any
|
|
|
|
// writer releases the lock, or a reader fully
|
|
|
|
// releases the lock. It may not be set to false
|
|
|
|
// by a reader that decrements the count to
|
|
|
|
// non-zero. protected by mutex spinlock
|
|
|
|
bool suppress_fatal_errors; // If true, try to proceed even in the face
|
|
|
|
// of broken invariants. This is used within
|
|
|
|
// fatal signal handlers to improve the
|
|
|
|
// chances of debug logging information being
|
|
|
|
// output successfully.
|
|
|
|
int priority; // Priority of thread (updated every so often).
|
|
|
|
|
|
|
|
// State values:
|
|
|
|
// kAvailable: This PerThreadSynch is available.
|
|
|
|
// kQueued: This PerThreadSynch is unavailable, it's currently queued on a
|
|
|
|
// Mutex or CondVar waistlist.
|
|
|
|
//
|
|
|
|
// Transitions from kQueued to kAvailable require a release
|
|
|
|
// barrier. This is needed as a waiter may use "state" to
|
|
|
|
// independently observe that it's no longer queued.
|
|
|
|
//
|
|
|
|
// Transitions from kAvailable to kQueued require no barrier, they
|
|
|
|
// are externally ordered by the Mutex.
|
|
|
|
enum State {
|
|
|
|
kAvailable,
|
|
|
|
kQueued
|
|
|
|
};
|
|
|
|
std::atomic<State> state;
|
|
|
|
|
|
|
|
// The wait parameters of the current wait. waitp is null if the
|
|
|
|
// thread is not waiting. Transitions from null to non-null must
|
|
|
|
// occur before the enqueue commit point (state = kQueued in
|
|
|
|
// Enqueue() and CondVarEnqueue()). Transitions from non-null to
|
|
|
|
// null must occur after the wait is finished (state = kAvailable in
|
|
|
|
// Mutex::Block() and CondVar::WaitCommon()). This field may be
|
|
|
|
// changed only by the thread that describes this PerThreadSynch. A
|
|
|
|
// special case is Fer(), which calls Enqueue() on another thread,
|
|
|
|
// but with an identical SynchWaitParams pointer, thus leaving the
|
|
|
|
// pointer unchanged.
|
|
|
|
SynchWaitParams* waitp;
|
|
|
|
|
|
|
|
intptr_t readers; // Number of readers in mutex.
|
|
|
|
|
|
|
|
// When priority will next be read (cycles).
|
|
|
|
int64_t next_priority_read_cycles;
|
|
|
|
|
|
|
|
// Locks held; used during deadlock detection.
|
|
|
|
// Allocated in Synch_GetAllLocks() and freed in ReclaimThreadIdentity().
|
|
|
|
SynchLocksHeld *all_locks;
|
|
|
|
};
|
|
|
|
|
|
|
|
// The instances of this class are allocated in NewThreadIdentity() with an
|
|
|
|
// alignment of PerThreadSynch::kAlignment.
|
|
|
|
struct ThreadIdentity {
|
|
|
|
// Must be the first member. The Mutex implementation requires that
|
|
|
|
// the PerThreadSynch object associated with each thread is
|
|
|
|
// PerThreadSynch::kAlignment aligned. We provide this alignment on
|
|
|
|
// ThreadIdentity itself.
|
|
|
|
PerThreadSynch per_thread_synch;
|
|
|
|
|
|
|
|
// Private: Reserved for absl::synchronization_internal::Waiter.
|
|
|
|
struct WaiterState {
|
|
|
|
char data[128];
|
|
|
|
} waiter_state;
|
|
|
|
|
|
|
|
// Used by PerThreadSem::{Get,Set}ThreadBlockedCounter().
|
|
|
|
std::atomic<int>* blocked_count_ptr;
|
|
|
|
|
|
|
|
// The following variables are mostly read/written just by the
|
|
|
|
// thread itself. The only exception is that these are read by
|
|
|
|
// a ticker thread as a hint.
|
|
|
|
std::atomic<int> ticker; // Tick counter, incremented once per second.
|
|
|
|
std::atomic<int> wait_start; // Ticker value when thread started waiting.
|
|
|
|
std::atomic<bool> is_idle; // Has thread become idle yet?
|
|
|
|
|
|
|
|
ThreadIdentity* next;
|
|
|
|
};
|
|
|
|
|
|
|
|
// Returns the ThreadIdentity object representing the calling thread; guaranteed
|
|
|
|
// to be unique for its lifetime. The returned object will remain valid for the
|
|
|
|
// program's lifetime; although it may be re-assigned to a subsequent thread.
|
|
|
|
// If one does not exist, return nullptr instead.
|
|
|
|
//
|
|
|
|
// Does not malloc(*), and is async-signal safe.
|
|
|
|
// [*] Technically pthread_setspecific() does malloc on first use; however this
|
|
|
|
// is handled internally within tcmalloc's initialization already.
|
|
|
|
//
|
|
|
|
// New ThreadIdentity objects can be constructed and associated with a thread
|
|
|
|
// by calling GetOrCreateCurrentThreadIdentity() in per-thread-sem.h.
|
|
|
|
ThreadIdentity* CurrentThreadIdentityIfPresent();
|
|
|
|
|
|
|
|
using ThreadIdentityReclaimerFunction = void (*)(void*);
|
|
|
|
|
|
|
|
// Sets the current thread identity to the given value. 'reclaimer' is a
|
|
|
|
// pointer to the global function for cleaning up instances on thread
|
|
|
|
// destruction.
|
|
|
|
void SetCurrentThreadIdentity(ThreadIdentity* identity,
|
|
|
|
ThreadIdentityReclaimerFunction reclaimer);
|
|
|
|
|
|
|
|
// Removes the currently associated ThreadIdentity from the running thread.
|
|
|
|
// This must be called from inside the ThreadIdentityReclaimerFunction, and only
|
|
|
|
// from that function.
|
|
|
|
void ClearCurrentThreadIdentity();
|
|
|
|
|
|
|
|
// May be chosen at compile time via: -DABSL_FORCE_THREAD_IDENTITY_MODE=<mode
|
|
|
|
// index>
|
|
|
|
#ifdef ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC
|
|
|
|
#error ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC cannot be direcly set
|
|
|
|
#else
|
|
|
|
#define ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC 0
|
|
|
|
#endif
|
|
|
|
|
|
|
|
#ifdef ABSL_THREAD_IDENTITY_MODE_USE_TLS
|
|
|
|
#error ABSL_THREAD_IDENTITY_MODE_USE_TLS cannot be direcly set
|
|
|
|
#else
|
|
|
|
#define ABSL_THREAD_IDENTITY_MODE_USE_TLS 1
|
|
|
|
#endif
|
|
|
|
|
|
|
|
#ifdef ABSL_THREAD_IDENTITY_MODE_USE_CPP11
|
|
|
|
#error ABSL_THREAD_IDENTITY_MODE_USE_CPP11 cannot be direcly set
|
|
|
|
#else
|
|
|
|
#define ABSL_THREAD_IDENTITY_MODE_USE_CPP11 2
|
|
|
|
#endif
|
|
|
|
|
|
|
|
#ifdef ABSL_THREAD_IDENTITY_MODE
|
|
|
|
#error ABSL_THREAD_IDENTITY_MODE cannot be direcly set
|
|
|
|
#elif defined(ABSL_FORCE_THREAD_IDENTITY_MODE)
|
|
|
|
#define ABSL_THREAD_IDENTITY_MODE ABSL_FORCE_THREAD_IDENTITY_MODE
|
|
|
|
#elif defined(_WIN32) && !defined(__MINGW32__)
|
|
|
|
#define ABSL_THREAD_IDENTITY_MODE ABSL_THREAD_IDENTITY_MODE_USE_CPP11
|
|
|
|
#elif defined(__APPLE__) && defined(ABSL_HAVE_THREAD_LOCAL)
|
|
|
|
#define ABSL_THREAD_IDENTITY_MODE ABSL_THREAD_IDENTITY_MODE_USE_CPP11
|
|
|
|
#elif ABSL_PER_THREAD_TLS && defined(__GOOGLE_GRTE_VERSION__) && \
|
|
|
|
(__GOOGLE_GRTE_VERSION__ >= 20140228L)
|
|
|
|
// Support for async-safe TLS was specifically added in GRTEv4. It's not
|
|
|
|
// present in the upstream eglibc.
|
|
|
|
// Note: Current default for production systems.
|
|
|
|
#define ABSL_THREAD_IDENTITY_MODE ABSL_THREAD_IDENTITY_MODE_USE_TLS
|
|
|
|
#else
|
|
|
|
#define ABSL_THREAD_IDENTITY_MODE \
|
|
|
|
ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC
|
|
|
|
#endif
|
|
|
|
|
|
|
|
#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS || \
|
|
|
|
ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11
|
|
|
|
|
|
|
|
#if ABSL_PER_THREAD_TLS
|
|
|
|
ABSL_CONST_INIT extern ABSL_PER_THREAD_TLS_KEYWORD ThreadIdentity*
|
|
|
|
thread_identity_ptr;
|
|
|
|
#elif defined(ABSL_HAVE_THREAD_LOCAL)
|
|
|
|
ABSL_CONST_INIT extern thread_local ThreadIdentity* thread_identity_ptr;
|
|
|
|
#else
|
|
|
|
#error Thread-local storage not detected on this platform
|
|
|
|
#endif
|
|
|
|
|
|
|
|
// thread_local variables cannot be in headers exposed by DLLs. However, it is
|
|
|
|
// important for performance reasons in general that
|
|
|
|
// `CurrentThreadIdentityIfPresent` be inlined. This is not possible across a
|
|
|
|
// DLL boundary so, with DLLs, we opt to have the function not be inlined. Note
|
|
|
|
// that `CurrentThreadIdentityIfPresent` is declared above so we can exclude
|
|
|
|
// this entire inline definition when compiling as a DLL.
|
|
|
|
#if !defined(ABSL_BUILD_DLL) && !defined(ABSL_CONSUME_DLL)
|
|
|
|
inline ThreadIdentity* CurrentThreadIdentityIfPresent() {
|
|
|
|
return thread_identity_ptr;
|
|
|
|
}
|
|
|
|
#endif
|
|
|
|
|
|
|
|
#elif ABSL_THREAD_IDENTITY_MODE != \
|
|
|
|
ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC
|
|
|
|
#error Unknown ABSL_THREAD_IDENTITY_MODE
|
|
|
|
#endif
|
|
|
|
|
|
|
|
} // namespace base_internal
|
|
|
|
ABSL_NAMESPACE_END
|
|
|
|
} // namespace absl
|
|
|
|
|
|
|
|
#endif // ABSL_BASE_INTERNAL_THREAD_IDENTITY_H_
|