Assume CrossThreadRsh is always supported and drop the flag

src/rhi/qrhi.cpp

@@ -313,20 +313,6 @@ QT_BEGIN_NAMESPACE
     identically across backends, as long as this feature is reported as
     supported, are \l{QRhiGraphicsPipeline::LineStrip}{LineStrip} and
     \l{QRhiGraphicsPipeline::TriangleStrip}{TriangleStrip}.
-
-    \value CrossThreadResourceSharing Indicates that creating QRhi instances on
-    different threads with QRhiResourceSharingHost set is allowed. Backends
-    where the underlying graphics API cannot safely support using the same
-    device or context from multiple threads will report this feature as
-    unsupported. When not supported, creating a QRhi with a
-    QRhiResourceSharingHost when there are already other QRhi instances on
-    other threads associated with the same QRhiResourceSharingHost will behave
-    as if the QRhiResourceSharingHost was not set at all. Application and
-    framework design may need to take support for this feature into account:
-    making resources like textures visible to multiple QRhi instances is not
-    neccessarily possible, so the design should be flexible enough to allow
-    functioning in that case as well (by using per-QRhi resources instead of a
-    single shared one, and possibly duplicating work).
  */
 
 /*!
@@ -1178,7 +1164,7 @@ void QRhiResource::setName(const QByteArray &name)
     and renderbuffers. Most backends will not support other type of shareable
     resources.
 
-    \sa QRhiResourceSharingHost, QRhi::CrossThreadResourceSharing
+    \sa QRhiResourceSharingHost
  */
 bool QRhiResource::isShareable() const
 {
@@ -2615,14 +2601,6 @@ quint32 QRhiImplementation::approxByteSizeForTexture(QRhiTexture::Format format,
     then; if there are new QRhi instances created for the same resource sharing
     host later on then there is no issue, as long as, again, those are alive).
 
-    \note When creating QRhi instances on different threads, using
-    QRhiResourceSharingHost may not be supported, depending on the backend and
-    the underlying graphics API. Support for this is indicated by the
-    QRhi::CrossThreadResourceSharing flag. When not supported, attempting to
-    create a QRhi in such a threaded scenario with a QRhiResourceSharingHost
-    will lead to a warning and ignoring resource sharing altogether (as if
-    QRhiInitParams::resourceSharingHost was not set).
-
     \note The QRhiResourceSharingHost can be created on a thread that is
     different than the threads on which the associated QRhi instances will be
     created. It is however up to the application to organize those threads in a
@@ -2696,8 +2674,7 @@ quint32 QRhiImplementation::approxByteSizeForTexture(QRhiTexture::Format format,
     \note Moving the \c{tex->releaseAndDestroy()} call between the \c{delete
     rhi2} and \c{delete rsh} statements would be incorrect.
 
-    \sa QRhiResource::isShareable(), QRhi::CrossThreadResourceSharing,
-    QRhiInitParams, QRhi::create()
+    \sa QRhiResource::isShareable(), QRhiInitParams, QRhi::create()
  */
 
 /*!
@@ -2719,23 +2696,6 @@ QRhiResourceSharingHost::~QRhiResourceSharingHost()
     delete d;
 }
 
-bool QRhiResourceSharingHostPrivate::crossThreadDisallowCheck() const
-{
-    bool otherThreads = false;
-    for (QThread *t : qAsConst(rhiThreads)) {
-        if (t != QThread::currentThread()) {
-            otherThreads = true;
-            break;
-        }
-    }
-    if (otherThreads) {
-        qWarning("Attempted to set a QRhiResourceSharingHost with QRhi instances on different threads when "
-                 "QRhi::CrossThreadResourceSharing is not supported. Resource sharing will be disabled.");
-        return false;
-    }
-    return true;
-}
-
 /*!
     \internal
  */

src/rhi/qrhi.h

@@ -1164,8 +1164,7 @@ public:
         Timestamps,
         Instancing,
         CustomInstanceStepRate,
-        PrimitiveRestart,
-        CrossThreadResourceSharing
+        PrimitiveRestart
     };
 
     enum ResourceSizeLimit {

src/rhi/qrhid3d11.cpp

@@ -164,9 +164,6 @@ bool QRhiD3D11::create(QRhi::Flags flags)
 
     QMutexLocker lock(rsh ? &rsh->mtx : nullptr);
 
-//    if (!rsh->crossThreadDisallowCheck())
-//        rsh = nullptr;
-
     uint devFlags = 0;
     if (debugLayer)
         devFlags |= D3D11_CREATE_DEVICE_DEBUG;
@@ -241,7 +238,6 @@ bool QRhiD3D11::create(QRhi::Flags flags)
         qDebug("Attached to QRhiResourceSharingHost %p, currently %d other QRhi instances on ID3D11Device %p",
                rsh, rsh->rhiCount, dev);
         rsh->rhiCount += 1;
-        rsh->rhiThreads.append(QThread::currentThread());
     }
 
     return true;
@@ -272,9 +268,7 @@ void QRhiD3D11::destroy()
     }
 
     if (rsh) {
-        rsh->rhiCount -= 1;
-        rsh->rhiThreads.removeOne(QThread::currentThread());
-        if (rsh->rhiCount == 0) {
+        if (--rsh->rhiCount == 0) {
             if (rsh->d_d3d11.context) {
                 reinterpret_cast<ID3D11DeviceContext1 *>(rsh->d_d3d11.context)->Release();
                 rsh->d_d3d11.context = nullptr;
@@ -392,8 +386,6 @@ bool QRhiD3D11::isFeatureSupported(QRhi::Feature feature) const
         return true;
     case QRhi::PrimitiveRestart:
         return true;
-    case QRhi::CrossThreadResourceSharing:
-        return true;
     default:
         Q_UNREACHABLE();
         return false;

src/rhi/qrhigles2.cpp

@@ -295,7 +295,6 @@ bool QRhiGles2::create(QRhi::Flags flags)
     if (rsh) {
         qDebug("Attached to QRhiResourceSharingHost %p, currently %d other QRhi instances", rsh, rsh->rhiCount);
         rsh->rhiCount += 1;
-        rsh->rhiThreads.append(QThread::currentThread());
     }
 
     return true;
@@ -319,9 +318,7 @@ void QRhiGles2::destroy()
     }
 
     if (rsh) {
-        rsh->rhiCount -= 1;
-        rsh->rhiThreads.removeOne(QThread::currentThread());
-        if (rsh->rhiCount == 0) {
+        if (--rsh->rhiCount == 0) {
             delete rsh->d_gles2.dummyShareContext;
             rsh->d_gles2.dummyShareContext = nullptr;
         }
@@ -466,8 +463,6 @@ bool QRhiGles2::isFeatureSupported(QRhi::Feature feature) const
         return false;
     case QRhi::PrimitiveRestart:
         return false; // say no to madness
-    case QRhi::CrossThreadResourceSharing:
-        return true;
     default:
         Q_UNREACHABLE();
         return false;

src/rhi/qrhimetal.mm

@@ -453,8 +453,6 @@ bool QRhiMetal::isFeatureSupported(QRhi::Feature feature) const
         return true;
     case QRhi::PrimitiveRestart:
         return true;
-    case QRhi::CrossThreadResourceSharing:
-        return true;
     default:
         Q_UNREACHABLE();
         return false;

src/rhi/qrhirsh_p.h

@@ -57,7 +57,6 @@
 #include "qrhimetal.h"
 #endif
 
-#include <QThread>
 #include <QMutex>
 
 QT_BEGIN_NAMESPACE
@@ -66,11 +65,9 @@ class Q_RHI_PRIVATE_EXPORT QRhiResourceSharingHostPrivate
 {
 public:
     static QRhiResourceSharingHostPrivate *get(QRhiResourceSharingHost *h) { return h->d; }
-    bool crossThreadDisallowCheck() const;
 
     QMutex mtx;
     int rhiCount = 0;
-    QVector<QThread *> rhiThreads;
 
 #ifndef QT_NO_OPENGL
     struct {

src/rhi/qrhivulkan.cpp

@@ -518,7 +518,6 @@ bool QRhiVulkan::create(QRhi::Flags flags)
         qDebug("Attached to QRhiResourceSharingHost %p, currently %d other QRhi instances on VkDevice %p",
                rsh, rsh->rhiCount, dev);
         rsh->rhiCount += 1;
-        rsh->rhiThreads.append(QThread::currentThread());
         if (rshWantsDevice) {
             rsh->d_vulkan.physDev = physDev;
             rsh->d_vulkan.dev = dev;
@@ -591,9 +590,7 @@ void QRhiVulkan::destroy()
     df = nullptr;
 
     if (rsh) {
-        rsh->rhiCount -= 1;
-        rsh->rhiThreads.removeOne(QThread::currentThread());
-        if (rsh->rhiCount == 0) {
+        if (--rsh->rhiCount == 0) {
             // all associated QRhi instances are gone for the rsh, time to clean up
             rsh->d_vulkan.df->vkDeviceWaitIdle(rsh->d_vulkan.dev);
             if (rsh->d_vulkan.releaseQueue) {
@@ -3007,8 +3004,6 @@ bool QRhiVulkan::isFeatureSupported(QRhi::Feature feature) const
         return vertexAttribDivisorAvailable;
     case QRhi::PrimitiveRestart:
         return true;
-    case QRhi::CrossThreadResourceSharing:
-        return true;
     default:
         Q_UNREACHABLE();
         return false;

todo.txt

 res.sh.: gl
 res.sh.: mtl
 res.sh.: example to show read/write same texture
+threading with rsh with resource - more external sync needed
 advanced blend modes
 gl: tex formats (texture, readback)
 gl: srgb