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       1                 :            : // Copyright (c) 2009-2010 Satoshi Nakamoto
       2                 :            : // Copyright (c) 2009-2020 The Bitcoin Core developers
       3                 :            : // Distributed under the MIT software license, see the accompanying
       4                 :            : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       5                 :            : 
       6                 :            : #ifndef BITCOIN_THREADSAFETY_H
       7                 :            : #define BITCOIN_THREADSAFETY_H
       8                 :            : 
       9                 :            : #include <mutex>
      10                 :            : 
      11                 :            : #ifdef __clang__
      12                 :            : // TL;DR Add GUARDED_BY(mutex) to member variables. The others are
      13                 :            : // rarely necessary. Ex: int nFoo GUARDED_BY(cs_foo);
      14                 :            : //
      15                 :            : // See https://clang.llvm.org/docs/ThreadSafetyAnalysis.html
      16                 :            : // for documentation.  The clang compiler can do advanced static analysis
      17                 :            : // of locking when given the -Wthread-safety option.
      18                 :            : #define LOCKABLE __attribute__((lockable))
      19                 :            : #define SCOPED_LOCKABLE __attribute__((scoped_lockable))
      20                 :            : #define GUARDED_BY(x) __attribute__((guarded_by(x)))
      21                 :            : #define PT_GUARDED_BY(x) __attribute__((pt_guarded_by(x)))
      22                 :            : #define ACQUIRED_AFTER(...) __attribute__((acquired_after(__VA_ARGS__)))
      23                 :            : #define ACQUIRED_BEFORE(...) __attribute__((acquired_before(__VA_ARGS__)))
      24                 :            : #define EXCLUSIVE_LOCK_FUNCTION(...) __attribute__((exclusive_lock_function(__VA_ARGS__)))
      25                 :            : #define SHARED_LOCK_FUNCTION(...) __attribute__((shared_lock_function(__VA_ARGS__)))
      26                 :            : #define EXCLUSIVE_TRYLOCK_FUNCTION(...) __attribute__((exclusive_trylock_function(__VA_ARGS__)))
      27                 :            : #define SHARED_TRYLOCK_FUNCTION(...) __attribute__((shared_trylock_function(__VA_ARGS__)))
      28                 :            : #define UNLOCK_FUNCTION(...) __attribute__((unlock_function(__VA_ARGS__)))
      29                 :            : #define LOCK_RETURNED(x) __attribute__((lock_returned(x)))
      30                 :            : #define LOCKS_EXCLUDED(...) __attribute__((locks_excluded(__VA_ARGS__)))
      31                 :            : #define EXCLUSIVE_LOCKS_REQUIRED(...) __attribute__((exclusive_locks_required(__VA_ARGS__)))
      32                 :            : #define SHARED_LOCKS_REQUIRED(...) __attribute__((shared_locks_required(__VA_ARGS__)))
      33                 :            : #define NO_THREAD_SAFETY_ANALYSIS __attribute__((no_thread_safety_analysis))
      34                 :            : #define ASSERT_EXCLUSIVE_LOCK(...) __attribute__((assert_exclusive_lock(__VA_ARGS__)))
      35                 :            : #else
      36                 :            : #define LOCKABLE
      37                 :            : #define SCOPED_LOCKABLE
      38                 :            : #define GUARDED_BY(x)
      39                 :            : #define PT_GUARDED_BY(x)
      40                 :            : #define ACQUIRED_AFTER(...)
      41                 :            : #define ACQUIRED_BEFORE(...)
      42                 :            : #define EXCLUSIVE_LOCK_FUNCTION(...)
      43                 :            : #define SHARED_LOCK_FUNCTION(...)
      44                 :            : #define EXCLUSIVE_TRYLOCK_FUNCTION(...)
      45                 :            : #define SHARED_TRYLOCK_FUNCTION(...)
      46                 :            : #define UNLOCK_FUNCTION(...)
      47                 :            : #define LOCK_RETURNED(x)
      48                 :            : #define LOCKS_EXCLUDED(...)
      49                 :            : #define EXCLUSIVE_LOCKS_REQUIRED(...)
      50                 :            : #define SHARED_LOCKS_REQUIRED(...)
      51                 :            : #define NO_THREAD_SAFETY_ANALYSIS
      52                 :            : #define ASSERT_EXCLUSIVE_LOCK(...)
      53                 :            : #endif // __GNUC__
      54                 :            : 
      55                 :            : // StdMutex provides an annotated version of std::mutex for us,
      56                 :            : // and should only be used when sync.h Mutex/LOCK/etc are not usable.
      57                 :          0 : class LOCKABLE StdMutex : public std::mutex
      58                 :            : {
      59                 :            : public:
      60                 :            : #ifdef __clang__
      61                 :            :     //! For negative capabilities in the Clang Thread Safety Analysis.
      62                 :            :     //! A negative requirement uses the EXCLUSIVE_LOCKS_REQUIRED attribute, in conjunction
      63                 :            :     //! with the ! operator, to indicate that a mutex should not be held.
      64                 :            :     const StdMutex& operator!() const { return *this; }
      65                 :            : #endif // __clang__
      66                 :            : };
      67                 :            : 
      68                 :            : // StdLockGuard provides an annotated version of std::lock_guard for us,
      69                 :            : // and should only be used when sync.h Mutex/LOCK/etc are not usable.
      70                 :            : class SCOPED_LOCKABLE StdLockGuard : public std::lock_guard<StdMutex>
      71                 :            : {
      72                 :            : public:
      73                 :          0 :     explicit StdLockGuard(StdMutex& cs) EXCLUSIVE_LOCK_FUNCTION(cs) : std::lock_guard<StdMutex>(cs) {}
      74                 :          0 :     ~StdLockGuard() UNLOCK_FUNCTION() {}
      75                 :            : };
      76                 :            : 
      77                 :            : #endif // BITCOIN_THREADSAFETY_H