Race condition fix

 Bug: 4232693

Change-Id: I273671aea3dc379858f11546e6459fd9e1443d4f

3 files changed, 16 insertions, 4 deletions

diff --git a/WebCore/platform/graphics/android/BackedDoubleBufferedTexture.cpp b/WebCore/platform/graphics/android/BackedDoubleBufferedTexture.cpp
index 63c9806..dc0962c 100644
--- a/WebCore/platform/graphics/android/BackedDoubleBufferedTexture.cpp
+++ b/WebCore/platform/graphics/android/BackedDoubleBufferedTexture.cpp
@@ -202,6 +202,20 @@ bool BackedDoubleBufferedTexture::acquire(TextureOwner* owner)
     return setOwner(owner);
 }
 
+bool BackedDoubleBufferedTexture::tryAcquire(TextureOwner* owner, TiledPage* currentPage, TiledPage* nextPage)
+{
+    m_busyLock.lock();
+    if (!m_busy
+        && m_owner
+        && m_owner->page() != currentPage
+        && m_owner->page() != nextPage) {
+        m_busyLock.unlock();
+        return this->acquire(owner);
+    }
+    m_busyLock.unlock();
+    return false;
+}
+
 bool BackedDoubleBufferedTexture::setOwner(TextureOwner* owner)
 {
     // if the writable texture is busy (i.e. currently being written to) then we
diff --git a/WebCore/platform/graphics/android/BackedDoubleBufferedTexture.h b/WebCore/platform/graphics/android/BackedDoubleBufferedTexture.h
index f612114..8bfae59 100644
--- a/WebCore/platform/graphics/android/BackedDoubleBufferedTexture.h
+++ b/WebCore/platform/graphics/android/BackedDoubleBufferedTexture.h
@@ -90,6 +90,7 @@ public:
     // returns false if ownership cannot be transferred because the tile is busy
     bool acquire(TextureOwner* owner);
     bool release(TextureOwner* owner);
+    bool tryAcquire(TextureOwner* owner, TiledPage* currentPage, TiledPage* nextPage);
 
     // set the texture owner if not busy. Return false if busy, true otherwise.
     bool setOwner(TextureOwner* owner);
diff --git a/WebCore/platform/graphics/android/TilesManager.cpp b/WebCore/platform/graphics/android/TilesManager.cpp
index bff1551..34d0546 100644
--- a/WebCore/platform/graphics/android/TilesManager.cpp
+++ b/WebCore/platform/graphics/android/TilesManager.cpp
@@ -201,10 +201,7 @@ BackedDoubleBufferedTexture* TilesManager::getAvailableTexture(BaseTile* owner)
     TiledPage* nextPage = currentPage->sibling();
     for (unsigned int i = 0; i < max; i++) {
         BackedDoubleBufferedTexture* texture = m_textures[i];
-        if (texture->owner()
-            && texture->owner()->page() != currentPage
-            && texture->owner()->page() != nextPage
-            && texture->acquire(owner)) {
+        if (texture->tryAcquire(owner, currentPage, nextPage)) {
             XLOG("grab a texture that wasn't ours, (%x != %x) at %d => texture %x",
                  owner->page(), texture->owner()->page(), i, texture);
             texture->setUsedLevel(0);