File indexing completed on 2024-04-28 05:30:39

 /*
     SPDX-FileCopyrightText: 2014 Fredrik Höglund <fredrik@kde.org>
 
     Explicit command stream synchronization based on the sample implementation by James Jones <jajones@nvidia.com>,
     SPDX-FileCopyrightText: 2011 NVIDIA Corporation
 
     SPDX-License-Identifier: GPL-2.0-or-later
 */
 #include "x11syncmanager.h"
 #include "compositor.h"
 #include "core/outputbackend.h"
 #include "core/renderbackend.h"
 #include "main.h"
 #include "scene/workspacescene.h"
 #include "utils/common.h"
 
 #include "opengl/glplatform.h"
 
 namespace KWin
 {
 
 X11SyncObject::X11SyncObject()
 {
     m_state = Ready;
 
     xcb_connection_t *const connection = kwinApp()->x11Connection();
     m_fence = xcb_generate_id(connection);
     xcb_sync_create_fence(connection, kwinApp()->x11RootWindow(), m_fence, false);
     xcb_flush(connection);
 
     m_sync = glImportSyncEXT(GL_SYNC_X11_FENCE_EXT, m_fence, 0);
 }
 
 X11SyncObject::~X11SyncObject()
 {
     xcb_connection_t *const connection = kwinApp()->x11Connection();
     // If glDeleteSync is called before the xcb fence is signalled
     // the nvidia driver (the only one to implement GL_SYNC_X11_FENCE_EXT)
     // deadlocks waiting for the fence to be signalled.
     // To avoid this, make sure the fence is signalled before
     // deleting the sync.
     if (m_state == Resetting || m_state == Ready) {
         trigger();
         // The flush is necessary!
         // The trigger command needs to be sent to the X server.
         xcb_flush(connection);
     }
     xcb_sync_destroy_fence(connection, m_fence);
     glDeleteSync(m_sync);
 
     if (m_state == Resetting) {
         xcb_discard_reply(connection, m_reset_cookie.sequence);
     }
 }
 
 void X11SyncObject::trigger()
 {
     Q_ASSERT(m_state == Ready || m_state == Resetting);
 
     // Finish resetting the fence if necessary
     if (m_state == Resetting) {
         finishResetting();
     }
 
     xcb_sync_trigger_fence(kwinApp()->x11Connection(), m_fence);
     m_state = TriggerSent;
 }
 
 void X11SyncObject::wait()
 {
     if (m_state != TriggerSent) {
         return;
     }
 
     glWaitSync(m_sync, 0, GL_TIMEOUT_IGNORED);
     m_state = Waiting;
 }
 
 bool X11SyncObject::finish()
 {
     if (m_state == Done) {
         return true;
     }
 
     // Note: It is possible that we never inserted a wait for the fence.
     //       This can happen if we ended up not rendering the damaged
     //       window because it is fully occluded.
     Q_ASSERT(m_state == TriggerSent || m_state == Waiting);
 
     // Check if the fence is signaled
     GLint value;
     glGetSynciv(m_sync, GL_SYNC_STATUS, 1, nullptr, &value);
 
     if (value != GL_SIGNALED) {
         qCDebug(KWIN_CORE) << "Waiting for X fence to finish";
 
         // Wait for the fence to become signaled with a one second timeout
         const GLenum result = glClientWaitSync(m_sync, 0, 1000000000);
 
         switch (result) {
         case GL_TIMEOUT_EXPIRED:
             qCWarning(KWIN_CORE) << "Timeout while waiting for X fence";
             return false;
 
         case GL_WAIT_FAILED:
             qCWarning(KWIN_CORE) << "glClientWaitSync() failed";
             return false;
         }
     }
 
     m_state = Done;
     return true;
 }
 
 void X11SyncObject::reset()
 {
     Q_ASSERT(m_state == Done);
 
     xcb_connection_t *const connection = kwinApp()->x11Connection();
 
     // Send the reset request along with a sync request.
     // We use the cookie to ensure that the server has processed the reset
     // request before we trigger the fence and call glWaitSync().
     // Otherwise there is a race condition between the reset finishing and
     // the glWaitSync() call.
     xcb_sync_reset_fence(connection, m_fence);
     m_reset_cookie = xcb_get_input_focus(connection);
     xcb_flush(connection);
 
     m_state = Resetting;
 }
 
 void X11SyncObject::finishResetting()
 {
     Q_ASSERT(m_state == Resetting);
     free(xcb_get_input_focus_reply(kwinApp()->x11Connection(), m_reset_cookie, nullptr));
     m_state = Ready;
 }
 
 X11SyncManager *X11SyncManager::create()
 {
     if (kwinApp()->operationMode() != Application::OperationModeX11) {
         return nullptr;
     }
 
     if (Compositor::self()->backend()->compositingType() != OpenGLCompositing) {
         return nullptr;
     }
 
     GLPlatform *glPlatform = GLPlatform::instance();
     const bool haveSyncObjects = glPlatform->isGLES()
         ? hasGLVersion(3, 0)
         : hasGLVersion(3, 2) || hasGLExtension("GL_ARB_sync");
 
     if (hasGLExtension("GL_EXT_x11_sync_object") && haveSyncObjects) {
         const QString useExplicitSync = qEnvironmentVariable("KWIN_EXPLICIT_SYNC");
 
         if (useExplicitSync != QLatin1String("0")) {
             qCDebug(KWIN_CORE) << "Initializing fences for synchronization with the X command stream";
             return new X11SyncManager;
         } else {
             qCDebug(KWIN_CORE) << "Explicit synchronization with the X command stream disabled by environment variable";
         }
     }
     return nullptr;
 }
 
 X11SyncManager::X11SyncManager()
 {
     for (int i = 0; i < MaxFences; ++i) {
         m_fences.append(new X11SyncObject);
     }
 }
 
 X11SyncManager::~X11SyncManager()
 {
     Compositor::self()->scene()->makeOpenGLContextCurrent();
     qDeleteAll(m_fences);
 }
 
 bool X11SyncManager::endFrame()
 {
     if (!m_currentFence) {
         return true;
     }
 
     for (int i = 0; i < std::min<int>(2, m_fences.count() - 1); i++) {
         const int index = (m_next + i) % m_fences.count();
         X11SyncObject *fence = m_fences[index];
 
         switch (fence->state()) {
         case X11SyncObject::Ready:
             break;
 
         case X11SyncObject::TriggerSent:
         case X11SyncObject::Waiting:
             if (!fence->finish()) {
                 return false;
             }
             fence->reset();
             break;
 
         // Should not happen in practice since we always reset the fence after finishing it
         case X11SyncObject::Done:
             fence->reset();
             break;
 
         case X11SyncObject::Resetting:
             fence->finishResetting();
             break;
         }
     }
 
     m_currentFence = nullptr;
     return true;
 }
 
 void X11SyncManager::triggerFence()
 {
     m_currentFence = m_fences[m_next];
     m_next = (m_next + 1) % m_fences.count();
     m_currentFence->trigger();
 }
 
 void X11SyncManager::insertWait()
 {
     if (m_currentFence && m_currentFence->state() != X11SyncObject::Waiting) {
         m_currentFence->wait();
     }
 }
 
 } // namespace KWin