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      1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef BASE_SYNCHRONIZATION_LOCK_IMPL_H_
      6 #define BASE_SYNCHRONIZATION_LOCK_IMPL_H_
      7 
      8 #include "base/base_export.h"
      9 #include "base/logging.h"
     10 #include "base/macros.h"
     11 #include "build/build_config.h"
     12 
     13 #if defined(OS_WIN)
     14 #include "base/win/windows_types.h"
     15 #elif defined(OS_POSIX) || defined(OS_FUCHSIA)
     16 #include <errno.h>
     17 #include <pthread.h>
     18 #endif
     19 
     20 namespace base {
     21 namespace internal {
     22 
     23 // This class implements the underlying platform-specific spin-lock mechanism
     24 // used for the Lock class.  Most users should not use LockImpl directly, but
     25 // should instead use Lock.
     26 class BASE_EXPORT LockImpl {
     27  public:
     28 #if defined(OS_WIN)
     29   using NativeHandle = CHROME_SRWLOCK;
     30 #elif defined(OS_POSIX) || defined(OS_FUCHSIA)
     31   using NativeHandle = pthread_mutex_t;
     32 #endif
     33 
     34   LockImpl();
     35   ~LockImpl();
     36 
     37   // If the lock is not held, take it and return true.  If the lock is already
     38   // held by something else, immediately return false.
     39   bool Try();
     40 
     41   // Take the lock, blocking until it is available if necessary.
     42   void Lock();
     43 
     44   // Release the lock.  This must only be called by the lock's holder: after
     45   // a successful call to Try, or a call to Lock.
     46   inline void Unlock();
     47 
     48   // Return the native underlying lock.
     49   // TODO(awalker): refactor lock and condition variables so that this is
     50   // unnecessary.
     51   NativeHandle* native_handle() { return &native_handle_; }
     52 
     53 #if defined(OS_POSIX) || defined(OS_FUCHSIA)
     54   // Whether this lock will attempt to use priority inheritance.
     55   static bool PriorityInheritanceAvailable();
     56 #endif
     57 
     58  private:
     59   NativeHandle native_handle_;
     60 
     61   DISALLOW_COPY_AND_ASSIGN(LockImpl);
     62 };
     63 
     64 #if defined(OS_WIN)
     65 void LockImpl::Unlock() {
     66   ::ReleaseSRWLockExclusive(reinterpret_cast<PSRWLOCK>(&native_handle_));
     67 }
     68 #elif defined(OS_POSIX) || defined(OS_FUCHSIA)
     69 void LockImpl::Unlock() {
     70   int rv = pthread_mutex_unlock(&native_handle_);
     71   DCHECK_EQ(rv, 0) << ". " << strerror(rv);
     72 }
     73 #endif
     74 
     75 }  // namespace internal
     76 }  // namespace base
     77 
     78 #endif  // BASE_SYNCHRONIZATION_LOCK_IMPL_H_
     79