Bug 895358 - Part 1, Adding POSIX cross process mutex to support progressive tile rendering in B2G; r=khuey

ipc/glue/CrossProcessMutex.h

@@ -9,6 +9,12 @@
 #include "base/process.h"
 #include "mozilla/Mutex.h"
 
+#if defined(OS_LINUX)
+#include <pthread.h>
+#include "SharedMemoryBasic.h"
+#include "mozilla/Atomics.h"
+#endif
+
 namespace IPC {
 template<typename T>
 struct ParamTraits;
@@ -27,6 +33,8 @@ struct ParamTraits;
 namespace mozilla {
 #ifdef XP_WIN
 typedef HANDLE CrossProcessMutexHandle;
+#elif defined(OS_LINUX)
+typedef mozilla::ipc::SharedMemoryBasic::Handle CrossProcessMutexHandle;
 #else
 // Stub for other platforms. We can't use uintptr_t here since different
 // processes could disagree on its size.
@@ -91,6 +99,10 @@ private:
 
 #ifdef XP_WIN
   HANDLE mMutex;
+#elif defined(OS_LINUX)
+  mozilla::ipc::SharedMemoryBasic* mSharedBuffer;
+  pthread_mutex_t* mMutex;
+  mozilla::Atomic<int32_t>* mCount;
 #endif
 };
 

ipc/glue/CrossProcessMutex_posix.cpp

@@ -0,0 +1,131 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "CrossProcessMutex.h"
+#include "mozilla/unused.h"
+#include "nsDebug.h"
+#include "nsTraceRefcnt.h"
+
+namespace {
+
+struct MutexData {
+  pthread_mutex_t mMutex;
+  mozilla::Atomic<int32_t> mCount;
+};
+
+}
+
+namespace mozilla {
+
+CrossProcessMutex::CrossProcessMutex(const char*)
+    : mSharedBuffer(nullptr)
+    , mMutex(nullptr)
+    , mCount(nullptr)
+{
+  mSharedBuffer = new ipc::SharedMemoryBasic;
+  if (!mSharedBuffer->Create(sizeof(MutexData))) {
+    MOZ_CRASH();
+  }
+
+  if (!mSharedBuffer->Map(sizeof(MutexData))) {
+    MOZ_CRASH();
+  }
+
+  MutexData* data = static_cast<MutexData*>(mSharedBuffer->memory());
+
+  if (!data) {
+    MOZ_CRASH();
+  }
+
+  mMutex = &(data->mMutex);
+  mCount = &(data->mCount);
+
+  *mCount = 1;
+
+  pthread_mutexattr_t mutexAttributes;
+  pthread_mutexattr_init(&mutexAttributes);
+  // Make the mutex reentrant so it behaves the same as a win32 mutex
+  if (pthread_mutexattr_settype(&mutexAttributes, PTHREAD_MUTEX_RECURSIVE)) {
+    MOZ_CRASH();
+  }
+  if (pthread_mutexattr_setpshared(&mutexAttributes, PTHREAD_PROCESS_SHARED)) {
+    MOZ_CRASH();
+  }
+
+  if (pthread_mutex_init(mMutex, &mutexAttributes)) {
+    MOZ_CRASH();
+  }
+
+  MOZ_COUNT_CTOR(CrossProcessMutex);
+}
+
+CrossProcessMutex::CrossProcessMutex(CrossProcessMutexHandle aHandle)
+    : mSharedBuffer(nullptr)
+    , mMutex(nullptr)
+    , mCount(nullptr)
+{
+  if (!ipc::SharedMemoryBasic::IsHandleValid(aHandle)) {
+    MOZ_CRASH();
+  }
+
+  mSharedBuffer = new ipc::SharedMemoryBasic(aHandle);
+
+  if (!mSharedBuffer->Map(sizeof(MutexData))) {
+    MOZ_CRASH();
+  }
+
+  MutexData* data = static_cast<MutexData*>(mSharedBuffer->memory());
+
+  if (!data) {
+    MOZ_CRASH();
+  }
+
+  mMutex = &(data->mMutex);
+  mCount = &(data->mCount);
+  (*mCount)++;
+
+  MOZ_COUNT_CTOR(CrossProcessMutex);
+}
+
+CrossProcessMutex::~CrossProcessMutex()
+{
+  int32_t count = --(*mCount);
+
+  if (count == 0) {
+    // Nothing can be done if the destroy fails so ignore return code.
+    unused << pthread_mutex_destroy(mMutex);
+  }
+
+  delete mSharedBuffer;
+  MOZ_COUNT_DTOR(CrossProcessMutex);
+}
+
+void
+CrossProcessMutex::Lock()
+{
+  MOZ_ASSERT(*mCount > 0, "Attempting to lock mutex with zero ref count");
+  pthread_mutex_lock(mMutex);
+}
+
+void
+CrossProcessMutex::Unlock()
+{
+  MOZ_ASSERT(*mCount > 0, "Attempting to unlock mutex with zero ref count");
+  pthread_mutex_unlock(mMutex);
+}
+
+CrossProcessMutexHandle
+CrossProcessMutex::ShareToProcess(base::ProcessHandle aHandle)
+{
+  CrossProcessMutexHandle result = ipc::SharedMemoryBasic::NULLHandle();
+
+  if (mSharedBuffer && !mSharedBuffer->ShareToProcess(aHandle, &result)) {
+    MOZ_CRASH();
+  }
+
+  return result;
+}
+
+}

ipc/glue/moz.build

@@ -35,7 +35,6 @@ if CONFIG['OS_ARCH'] == 'WINNT':
         'Transport_win.h',
     ]
     SOURCES += [
-        'CrossProcessMutex_windows.cpp',
         'SharedMemory_windows.cpp',
         'Transport_win.cpp',
         'WindowsMessageLoop.cpp',
@@ -45,11 +44,23 @@ else:
         'Transport_posix.h',
     ]
     UNIFIED_SOURCES += [
-        'CrossProcessMutex_unimplemented.cpp',
         'SharedMemory_posix.cpp',
         'Transport_posix.cpp',
     ]
 
+if CONFIG['OS_ARCH'] == 'WINNT':
+    SOURCES += [
+        'CrossProcessMutex_windows.cpp',
+    ]
+elif CONFIG['OS_ARCH'] == 'Linux':
+    UNIFIED_SOURCES += [
+        'CrossProcessMutex_posix.cpp',
+    ]
+else:
+    UNIFIED_SOURCES += [
+        'CrossProcessMutex_unimplemented.cpp',
+    ]
+
 # Android has its own,
 # almost-but-not-quite-compatible-with-POSIX-or-/dev/shm shared memory
 # impl.