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1 //
2 // Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
3 //
4 // Use of this source code is governed by a BSD-style license
5 // that can be found in the LICENSE file in the root of the source
6 // tree. An additional intellectual property rights grant can be found
7 // in the file PATENTS.  All contributing project authors may
8 // be found in the AUTHORS file in the root of the source tree.
9 //
10 // Borrowed from
11 // https://code.google.com/p/gperftools/source/browse/src/base/thread_annotations.h
12 // but adapted for clang attributes instead of the gcc.
13 //
14 // This header file contains the macro definitions for thread safety
15 // annotations that allow the developers to document the locking policies
16 // of their multi-threaded code. The annotations can also help program
17 // analysis tools to identify potential thread safety issues.
18 
19 #ifndef BASE_THREAD_ANNOTATIONS_H_
20 #define BASE_THREAD_ANNOTATIONS_H_
21 
22 #if defined(__clang__) && (!defined(SWIG))
23 #define THREAD_ANNOTATION_ATTRIBUTE__(x) __attribute__((x))
24 #else
25 #define THREAD_ANNOTATION_ATTRIBUTE__(x)  // no-op
26 #endif
27 
28 // Document if a shared variable/field needs to be protected by a lock.
29 // GUARDED_BY allows the user to specify a particular lock that should be
30 // held when accessing the annotated variable, while GUARDED_VAR only
31 // indicates a shared variable should be guarded (by any lock). GUARDED_VAR
32 // is primarily used when the client cannot express the name of the lock.
33 #define GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE__(guarded_by(x))
34 #define GUARDED_VAR THREAD_ANNOTATION_ATTRIBUTE__(guarded)
35 
36 // Document if the memory location pointed to by a pointer should be guarded
37 // by a lock when dereferencing the pointer. Similar to GUARDED_VAR,
38 // PT_GUARDED_VAR is primarily used when the client cannot express the name
39 // of the lock. Note that a pointer variable to a shared memory location
40 // could itself be a shared variable. For example, if a shared global pointer
41 // q, which is guarded by mu1, points to a shared memory location that is
42 // guarded by mu2, q should be annotated as follows:
43 //     int *q GUARDED_BY(mu1) PT_GUARDED_BY(mu2);
44 #define PT_GUARDED_BY(x) THREAD_ANNOTATION_ATTRIBUTE__(point_to_guarded_by(x))
45 #define PT_GUARDED_VAR THREAD_ANNOTATION_ATTRIBUTE__(point_to_guarded)
46 
47 // Document the acquisition order between locks that can be held
48 // simultaneously by a thread. For any two locks that need to be annotated
49 // to establish an acquisition order, only one of them needs the annotation.
50 // (i.e. You don't have to annotate both locks with both ACQUIRED_AFTER
51 // and ACQUIRED_BEFORE.)
52 #define ACQUIRED_AFTER(x) THREAD_ANNOTATION_ATTRIBUTE__(acquired_after(x))
53 #define ACQUIRED_BEFORE(x) THREAD_ANNOTATION_ATTRIBUTE__(acquired_before(x))
54 
55 // The following three annotations document the lock requirements for
56 // functions/methods.
57 
58 // Document if a function expects certain locks to be held before it is called
59 #define EXCLUSIVE_LOCKS_REQUIRED(...) \
60   THREAD_ANNOTATION_ATTRIBUTE__(exclusive_locks_required(__VA_ARGS__))
61 
62 #define SHARED_LOCKS_REQUIRED(...) \
63   THREAD_ANNOTATION_ATTRIBUTE__(shared_locks_required(__VA_ARGS__))
64 
65 // Document the locks acquired in the body of the function. These locks
66 // cannot be held when calling this function (as google3's Mutex locks are
67 // non-reentrant).
68 #define LOCKS_EXCLUDED(x) THREAD_ANNOTATION_ATTRIBUTE__(locks_excluded(x))
69 
70 // Document the lock the annotated function returns without acquiring it.
71 #define LOCK_RETURNED(x) THREAD_ANNOTATION_ATTRIBUTE__(lock_returned(x))
72 
73 // Document if a class/type is a lockable type (such as the Mutex class).
74 #define LOCKABLE THREAD_ANNOTATION_ATTRIBUTE__(lockable)
75 
76 // Document if a class is a scoped lockable type (such as the MutexLock class).
77 #define SCOPED_LOCKABLE THREAD_ANNOTATION_ATTRIBUTE__(scoped_lockable)
78 
79 // The following annotations specify lock and unlock primitives.
80 #define EXCLUSIVE_LOCK_FUNCTION(...) \
81   THREAD_ANNOTATION_ATTRIBUTE__(exclusive_lock_function(__VA_ARGS__))
82 
83 #define SHARED_LOCK_FUNCTION(...) \
84   THREAD_ANNOTATION_ATTRIBUTE__(shared_lock_function(__VA_ARGS__))
85 
86 #define EXCLUSIVE_TRYLOCK_FUNCTION(...) \
87   THREAD_ANNOTATION_ATTRIBUTE__(exclusive_trylock_function(__VA_ARGS__))
88 
89 #define SHARED_TRYLOCK_FUNCTION(...) \
90   THREAD_ANNOTATION_ATTRIBUTE__(shared_trylock_function(__VA_ARGS__))
91 
92 #define UNLOCK_FUNCTION(...) \
93   THREAD_ANNOTATION_ATTRIBUTE__(unlock_function(__VA_ARGS__))
94 
95 // An escape hatch for thread safety analysis to ignore the annotated function.
96 #define NO_THREAD_SAFETY_ANALYSIS \
97   THREAD_ANNOTATION_ATTRIBUTE__(no_thread_safety_analysis)
98 
99 #endif  // BASE_THREAD_ANNOTATIONS_H_
100