tvl-depot/absl/base/internal/thread_identity.h

242 lines
9.4 KiB
C
Raw Normal View History

2017-09-19 22:54:40 +02:00
// 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
2017-09-19 22:54:40 +02:00
//
// 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/internal/per_thread_tls.h"
namespace absl {
struct SynchLocksHeld;
struct SynchWaitParams;
namespace base_internal {
class SpinLock;
struct ThreadIdentity;
// Used by the implementation of absl::Mutex and absl::CondVar.
2017-09-19 22:54:40 +02:00
struct PerThreadSynch {
// The internal representation of absl::Mutex and absl::CondVar rely
2017-09-19 22:54:40 +02:00
// 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
2017-09-19 22:54:40 +02:00
// 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.
// 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;
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.
intptr_t readers; // Number of readers in mutex.
int priority; // Priority of thread (updated every so often).
// When priority will next be read (cycles).
int64_t next_priority_read_cycles;
// 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;
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 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;
// Locks held; used during deadlock detection.
// Allocated in Synch_GetAllLocks() and freed in ReclaimThreadIdentity().
SynchLocksHeld *all_locks;
};
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)
#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
extern ABSL_PER_THREAD_TLS_KEYWORD ThreadIdentity* thread_identity_ptr;
inline ThreadIdentity* CurrentThreadIdentityIfPresent() {
return thread_identity_ptr;
}
#elif ABSL_THREAD_IDENTITY_MODE != \
ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC
#error Unknown ABSL_THREAD_IDENTITY_MODE
#endif
} // namespace base_internal
} // namespace absl
Export of internal Abseil changes. -- bdce7e57e9e886eff1114d0266781b443f7ec639 by Derek Mauro <dmauro@google.com>: Change {Get|Set}EnvironmentVariable to {Get|Set}EnvironmentVariableA for compatibility with /DUNICODE. PiperOrigin-RevId: 239229514 -- 2276ed502326a044a84060d34eb19d499e3a3be2 by Derek Mauro <dmauro@google.com>: Import of CCTZ from GitHub. PiperOrigin-RevId: 239228622 -- a462efb970ff43b08a362ef2343fb75ac1295a50 by Derek Mauro <dmauro@google.com>: Adding linking of CoreFoundation to CMakeLists in absl/time. Import https://github.com/abseil/abseil-cpp/pull/280. Fix #283 PiperOrigin-RevId: 239220785 -- fc23327b97f940c682aae1956cf7a1bf87f88c06 by Derek Mauro <dmauro@google.com>: Add hermetic test script that uses Docker to build with a very recent version of gcc (8.3.0 today) with libstdc++ and bazel. PiperOrigin-RevId: 239220448 -- 418c08a8f6a53e63b84e39473035774417ca3aa7 by Derek Mauro <dmauro@google.com>: Disable part of the variant exeception safety test on move assignment when using versions of libstd++ that contain a bug. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87431#c7 PiperOrigin-RevId: 239062455 -- 799722217aeda79679577843c91d5be62cbcbb42 by Matt Calabrese <calabrese@google.com>: Add internal-only IsSwappable traits corresponding to std::is_swappable and std::is_nothrow_swappable, which are used with the swap implementations of optional and variant. PiperOrigin-RevId: 239049448 -- aa46a036038a3de5c68ac5e5d3b4bf76f818d2ea by CJ Johnson <johnsoncj@google.com>: Make InlinedVectorStorage constructor explicit PiperOrigin-RevId: 239044361 -- 17949715b3aa21c794701f69f2154e91b6acabc3 by CJ Johnson <johnsoncj@google.com>: Add absl namesapce to internal/inlined_vector.h PiperOrigin-RevId: 239030789 -- 834628325953078cc08ed10d23bb8890e5bec897 by Derek Mauro <dmauro@google.com>: Add test script that uses Docker to build Abseil with gcc-4.8, libstdc++, and cmake. PiperOrigin-RevId: 239028433 -- 80fe24149ed73ed2ced995ad1e372fb060c60427 by CJ Johnson <johnsoncj@google.com>: Factors data members of InlinedVector into an impl type called InlinedVectorStorage so that (in future changes) the contents of a vector can be grouped together with a single pointer. PiperOrigin-RevId: 239021086 -- 585331436d5d4d79f845e45dcf79d918a0dc6169 by Derek Mauro <dmauro@google.com>: Add -Wno-missing-field-initializers to gcc compiler flags. gcc-4.x has spurious missing field initializer warnings. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=36750 PiperOrigin-RevId: 239017217 -- 94602fe4e33ee3a552a7f2939c0f57a992f55075 by Abseil Team <absl-team@google.com>: Formatting fixes. PiperOrigin-RevId: 238983038 -- a1c1b63c08505574e0a8c491561840cecb2bb93e by Derek Mauro <dmauro@google.com>: Add hermetic test script that uses Docker to build with a very recent version of clang with libc++ and bazel. PiperOrigin-RevId: 238669118 -- e525f8d20bc2f79a0d69336b902f63858f3bff9d by Derek Mauro <dmauro@google.com>: Disable the test optionalTest.InPlaceTSFINAEBug until libc++ is updated. PiperOrigin-RevId: 238661703 -- f99a2a0b5ec424a059678f7f226600f137b4c74e by Derek Mauro <dmauro@google.com>: Correct the check for the FlatHashMap-Any test bug (list conditions instead of platforms when possible) PiperOrigin-RevId: 238653344 -- 777928035dbcbf39f361eb7d10dc3696822f692f by Jon Cohen <cohenjon@google.com>: Add install rules for Abseil CMake. These are attempted to be limited to in-project installation. This serves two purposes -- first it's morally the same as using Abseil in-source, except you don't have to rebuild us every time. Second, the presence of an install rule makes life massively simpler for package manager maintainers. Currently this doesn't install absl tests or testonly libraries. This can be added in a follow-up patch. Fixes #38, Fixes #80, Closes #182 PiperOrigin-RevId: 238645836 -- ded1c6ce697c191b7a6ff14572b3e6d183117b2c by Derek Mauro <dmauro@google.com>: Add hermetic test script that uses Docker to build with a very recent version of clang with libstdc++ and bazel. PiperOrigin-RevId: 238517815 GitOrigin-RevId: bdce7e57e9e886eff1114d0266781b443f7ec639 Change-Id: I6f745869cb8ef63851891ccac05ae9a7dd241c4f
2019-03-19 19:14:01 +01:00
2017-09-19 22:54:40 +02:00
#endif // ABSL_BASE_INTERNAL_THREAD_IDENTITY_H_