xpcom/threads/RWLock.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "mozilla/RWLock.h"
   8
   9 #ifdef XP_WIN
  10 #  include <windows.h>
  11
  12 static_assert(sizeof(SRWLOCK) <= sizeof(void*), "SRWLOCK is too big!");
  13
  14 #  define NativeHandle(m) (reinterpret_cast<SRWLOCK*>(&m))
  15 #else
  16 #  define NativeHandle(m) (&m)
  17 #endif
  18
  19 namespace mozilla {
  20
  21 RWLock::RWLock(const char* aName)
  22     : BlockingResourceBase(aName, eMutex)
  23 #ifdef DEBUG
  24       ,
  25       mOwningThread(nullptr)
  26 #endif
  27 {
  28 #ifdef XP_WIN
  29   InitializeSRWLock(NativeHandle(mRWLock));
  30 #else
  31   MOZ_RELEASE_ASSERT(pthread_rwlock_init(NativeHandle(mRWLock), nullptr) == 0,
  32                      "pthread_rwlock_init failed");
  33 #endif
  34 }
  35
  36 #ifdef DEBUG
  37 bool RWLock::LockedForWritingByCurrentThread() {
  38   return mOwningThread == PR_GetCurrentThread();
  39 }
  40 #endif
  41
  42 #ifndef XP_WIN
  43 RWLock::~RWLock() {
  44   MOZ_RELEASE_ASSERT(pthread_rwlock_destroy(NativeHandle(mRWLock)) == 0,
  45                      "pthread_rwlock_destroy failed");
  46 }
  47 #endif
  48
  49 bool RWLock::TryReadLockInternal() {
  50 #ifdef XP_WIN
  51   return TryAcquireSRWLockShared(NativeHandle(mRWLock));
  52 #else
  53   int rv = pthread_rwlock_tryrdlock(NativeHandle(mRWLock));
  54   // We allow EDEADLK here because it has been observed returned on macos when
  55   // the write lock is held by the current thread.
  56   MOZ_RELEASE_ASSERT(rv == 0 || rv == EBUSY || rv == EDEADLK,
  57                      "pthread_rwlock_tryrdlock failed");
  58   return rv == 0;
  59 #endif
  60 }
  61
  62 void RWLock::ReadLockInternal() {
  63 #ifdef XP_WIN
  64   AcquireSRWLockShared(NativeHandle(mRWLock));
  65 #else
  66   MOZ_RELEASE_ASSERT(pthread_rwlock_rdlock(NativeHandle(mRWLock)) == 0,
  67                      "pthread_rwlock_rdlock failed");
  68 #endif
  69 }
  70
  71 void RWLock::ReadUnlockInternal() {
  72 #ifdef XP_WIN
  73   ReleaseSRWLockShared(NativeHandle(mRWLock));
  74 #else
  75   MOZ_RELEASE_ASSERT(pthread_rwlock_unlock(NativeHandle(mRWLock)) == 0,
  76                      "pthread_rwlock_unlock failed");
  77 #endif
  78 }
  79
  80 bool RWLock::TryWriteLockInternal() {
  81 #ifdef XP_WIN
  82   return TryAcquireSRWLockExclusive(NativeHandle(mRWLock));
  83 #else
  84   int rv = pthread_rwlock_trywrlock(NativeHandle(mRWLock));
  85   // We allow EDEADLK here because it has been observed returned on macos when
  86   // the write lock is held by the current thread.
  87   MOZ_RELEASE_ASSERT(rv == 0 || rv == EBUSY || rv == EDEADLK,
  88                      "pthread_rwlock_trywrlock failed");
  89   return rv == 0;
  90 #endif
  91 }
  92
  93 void RWLock::WriteLockInternal() {
  94 #ifdef XP_WIN
  95   AcquireSRWLockExclusive(NativeHandle(mRWLock));
  96 #else
  97   MOZ_RELEASE_ASSERT(pthread_rwlock_wrlock(NativeHandle(mRWLock)) == 0,
  98                      "pthread_rwlock_wrlock failed");
  99 #endif
 100 }
 101
 102 void RWLock::WriteUnlockInternal() {
 103 #ifdef XP_WIN
 104   ReleaseSRWLockExclusive(NativeHandle(mRWLock));
 105 #else
 106   MOZ_RELEASE_ASSERT(pthread_rwlock_unlock(NativeHandle(mRWLock)) == 0,
 107                      "pthread_rwlock_unlock failed");
 108 #endif
 109 }
 110
 111 }  // namespace mozilla
 112
 113 #undef NativeHandle