diff options
Diffstat (limited to 'absl/base/thread_annotations.h')
| -rw-r--r-- | absl/base/thread_annotations.h | 247 |
1 files changed, 247 insertions, 0 deletions
diff --git a/absl/base/thread_annotations.h b/absl/base/thread_annotations.h new file mode 100644 index 000000000000..025a8548d5d7 --- /dev/null +++ b/absl/base/thread_annotations.h @@ -0,0 +1,247 @@ +// 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. +// +// ----------------------------------------------------------------------------- +// File: thread_annotations.h +// ----------------------------------------------------------------------------- +// +// This header file contains macro definitions for thread safety annotations +// that allow developers to document the locking policies of multi-threaded +// code. The annotations can also help program analysis tools to identify +// potential thread safety issues. +// +// +// These annotations are implemented using compiler attributes. Using the macros +// defined here instead of raw attributes allow for portability and future +// compatibility. +// +// When referring to mutexes in the arguments of the attributes, you should +// use variable names or more complex expressions (e.g. my_object->mutex_) +// that evaluate to a concrete mutex object whenever possible. If the mutex +// you want to refer to is not in scope, you may use a member pointer +// (e.g. &MyClass::mutex_) to refer to a mutex in some (unknown) object. +// + +#ifndef ABSL_BASE_THREAD_ANNOTATIONS_H_ +#define ABSL_BASE_THREAD_ANNOTATIONS_H_ +#if defined(__clang__) +#define THREAD_ANNOTATION_ATTRIBUTE__(x) __attribute__((x)) +#else +#define THREAD_ANNOTATION_ATTRIBUTE__(x) // no-op +#endif + +// GUARDED_BY() +// +// Documents if a shared variable/field needs to be protected by a mutex. +// GUARDED_BY() allows the user to specify a particular mutex that should be +// held when accessing the annotated variable. +// +// Example: +// +// Mutex mu; +// int p1 GUARDED_BY(mu); +#define GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE__(guarded_by(x)) +#define GUARDED_VAR THREAD_ANNOTATION_ATTRIBUTE__(guarded) + +// PT_GUARDED_BY() +// +// Documents if the memory location pointed to by a pointer should be guarded +// by a mutex when dereferencing the pointer. +// +// Example: +// Mutex mu; +// int *p1 PT_GUARDED_BY(mu); +// +// Note that a pointer variable to a shared memory location could itself be a +// shared variable. +// +// Example: +// +// // `q`, guarded by `mu1`, points to a shared memory location that is +// // guarded by `mu2`: +// int *q GUARDED_BY(mu1) PT_GUARDED_BY(mu2); +#define PT_GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded_by(x)) +#define PT_GUARDED_VAR THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded) + +// ACQUIRED_AFTER() / ACQUIRED_BEFORE() +// +// Documents the acquisition order between locks that can be held +// simultaneously by a thread. For any two locks that need to be annotated +// to establish an acquisition order, only one of them needs the annotation. +// (i.e. You don't have to annotate both locks with both ACQUIRED_AFTER +// and ACQUIRED_BEFORE.) +// +// Example: +// +// Mutex m1; +// Mutex m2 ACQUIRED_AFTER(m1); +#define ACQUIRED_AFTER(...) \ + THREAD_ANNOTATION_ATTRIBUTE__(acquired_after(__VA_ARGS__)) + +#define ACQUIRED_BEFORE(...) \ + THREAD_ANNOTATION_ATTRIBUTE__(acquired_before(__VA_ARGS__)) + +// EXCLUSIVE_LOCKS_REQUIRED() / SHARED_LOCKS_REQUIRED() +// +// Documents a function that expects a mutex to be held prior to entry. +// The mutex is expected to be held both on entry to, and exit from, the +// function. +// +// Example: +// +// Mutex mu1, mu2; +// int a GUARDED_BY(mu1); +// int b GUARDED_BY(mu2); +// +// void foo() EXCLUSIVE_LOCKS_REQUIRED(mu1, mu2) { ... }; +#define EXCLUSIVE_LOCKS_REQUIRED(...) \ + THREAD_ANNOTATION_ATTRIBUTE__(exclusive_locks_required(__VA_ARGS__)) + +#define SHARED_LOCKS_REQUIRED(...) \ + THREAD_ANNOTATION_ATTRIBUTE__(shared_locks_required(__VA_ARGS__)) + +// LOCKS_EXCLUDED() +// +// Documents the locks acquired in the body of the function. These locks +// cannot be held when calling this function (as Abseil's `Mutex` locks are +// non-reentrant). +#define LOCKS_EXCLUDED(...) \ + THREAD_ANNOTATION_ATTRIBUTE__(locks_excluded(__VA_ARGS__)) + +// LOCK_RETURNED() +// +// Documents a function that returns a mutex without acquiring it. For example, +// a public getter method that returns a pointer to a private mutex should +// be annotated with LOCK_RETURNED. +#define LOCK_RETURNED(x) \ + THREAD_ANNOTATION_ATTRIBUTE__(lock_returned(x)) + +// LOCKABLE +// +// Documents if a class/type is a lockable type (such as the `Mutex` class). +#define LOCKABLE \ + THREAD_ANNOTATION_ATTRIBUTE__(lockable) + +// SCOPED_LOCKABLE +// +// Documents if a class does RAII locking (such as the `MutexLock` class). +// The constructor should use `LOCK_FUNCTION()` to specify the mutex that is +// acquired, and the destructor should use `UNLOCK_FUNCTION()` with no +// arguments; the analysis will assume that the destructor unlocks whatever the +// constructor locked. +#define SCOPED_LOCKABLE \ + THREAD_ANNOTATION_ATTRIBUTE__(scoped_lockable) + +// EXCLUSIVE_LOCK_FUNCTION() +// +// Documents functions that acquire a lock in the body of a function, and do +// not release it. +#define EXCLUSIVE_LOCK_FUNCTION(...) \ + THREAD_ANNOTATION_ATTRIBUTE__(exclusive_lock_function(__VA_ARGS__)) + +// SHARED_LOCK_FUNCTION() +// +// Documents functions that acquire a shared (reader) lock in the body of a +// function, and do not release it. +#define SHARED_LOCK_FUNCTION(...) \ + THREAD_ANNOTATION_ATTRIBUTE__(shared_lock_function(__VA_ARGS__)) + +// UNLOCK_FUNCTION() +// +// Documents functions that expect a lock to be held on entry to the function, +// and release it in the body of the function. +#define UNLOCK_FUNCTION(...) \ + THREAD_ANNOTATION_ATTRIBUTE__(unlock_function(__VA_ARGS__)) + +// EXCLUSIVE_TRYLOCK_FUNCTION() / SHARED_TRYLOCK_FUNCTION() +// +// Documents functions that try to acquire a lock, and return success or failure +// (or a non-boolean value that can be interpreted as a boolean). +// The first argument should be `true` for functions that return `true` on +// success, or `false` for functions that return `false` on success. The second +// argument specifies the mutex that is locked on success. If unspecified, this +// mutex is assumed to be `this`. +#define EXCLUSIVE_TRYLOCK_FUNCTION(...) \ + THREAD_ANNOTATION_ATTRIBUTE__(exclusive_trylock_function(__VA_ARGS__)) + +#define SHARED_TRYLOCK_FUNCTION(...) \ + THREAD_ANNOTATION_ATTRIBUTE__(shared_trylock_function(__VA_ARGS__)) + +// ASSERT_EXCLUSIVE_LOCK() / ASSERT_SHARED_LOCK() +// +// Documents functions that dynamically check to see if a lock is held, and fail +// if it is not held. +#define ASSERT_EXCLUSIVE_LOCK(...) \ + THREAD_ANNOTATION_ATTRIBUTE__(assert_exclusive_lock(__VA_ARGS__)) + +#define ASSERT_SHARED_LOCK(...) \ + THREAD_ANNOTATION_ATTRIBUTE__(assert_shared_lock(__VA_ARGS__)) + +// NO_THREAD_SAFETY_ANALYSIS +// +// Turns off thread safety checking within the body of a particular function. +// This annotation is used to mark functions that are known to be correct, but +// the locking behavior is more complicated than the analyzer can handle. +#define NO_THREAD_SAFETY_ANALYSIS \ + THREAD_ANNOTATION_ATTRIBUTE__(no_thread_safety_analysis) + +//------------------------------------------------------------------------------ +// Tool-Supplied Annotations +//------------------------------------------------------------------------------ + +// TS_UNCHECKED should be placed around lock expressions that are not valid +// C++ syntax, but which are present for documentation purposes. These +// annotations will be ignored by the analysis. +#define TS_UNCHECKED(x) "" + +// TS_FIXME is used to mark lock expressions that are not valid C++ syntax. +// It is used by automated tools to mark and disable invalid expressions. +// The annotation should either be fixed, or changed to TS_UNCHECKED. +#define TS_FIXME(x) "" + +// Like NO_THREAD_SAFETY_ANALYSIS, this turns off checking within the body of +// a particular function. However, this attribute is used to mark functions +// that are incorrect and need to be fixed. It is used by automated tools to +// avoid breaking the build when the analysis is updated. +// Code owners are expected to eventually fix the routine. +#define NO_THREAD_SAFETY_ANALYSIS_FIXME NO_THREAD_SAFETY_ANALYSIS + +// Similar to NO_THREAD_SAFETY_ANALYSIS_FIXME, this macro marks a GUARDED_BY +// annotation that needs to be fixed, because it is producing thread safety +// warning. It disables the GUARDED_BY. +#define GUARDED_BY_FIXME(x) + +// Disables warnings for a single read operation. This can be used to avoid +// warnings when it is known that the read is not actually involved in a race, +// but the compiler cannot confirm that. +#define TS_UNCHECKED_READ(x) thread_safety_analysis::ts_unchecked_read(x) + + +namespace thread_safety_analysis { + +// Takes a reference to a guarded data member, and returns an unguarded +// reference. +template <typename T> +inline const T& ts_unchecked_read(const T& v) NO_THREAD_SAFETY_ANALYSIS { + return v; +} + +template <typename T> +inline T& ts_unchecked_read(T& v) NO_THREAD_SAFETY_ANALYSIS { + return v; +} + +} // namespace thread_safety_analysis + +#endif // ABSL_BASE_THREAD_ANNOTATIONS_H_ |