From 4ced73553ff2b2e7058ca86a3a9424dbe418dc0b Mon Sep 17 00:00:00 2001
From: fuleyi <fuleyi@uniontech.com>
Date: Wed, 24 Jun 2026 14:41:57 +0800
Subject: [PATCH] fix: handle X server disconnection gracefully
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When X server is killed (e.g., during init 3 to init 5 switch), libX11's
default I/O error handler calls exit(), bypassing Qt's normal shutdown.
This causes plugins to be destroyed during global destructors when
objects are already partially destroyed, leading to SIGSEGV.

Changes made:
1. Added X11 package dependency to CMakeLists.txt for Xlib headers and
linking
2. Implemented custom X I/O error handler that calls
QCoreApplication::quit() instead of exit()
3. Added SIGPIPE signal handler to prevent crashes when X pipe is broken
4. Handlers are installed only on xcb platform, not needed on Wayland

This ensures plugins receive aboutToQuit signal and can clean up
properly.

Log: Fixed crash when X server disconnects by installing custom error
handlers

Influence:
1. Test graceful shutdown when X server is terminated (init 3 to init
5 switch)
2. Verify no SIGSEGV occurs during X server disconnection
3. Confirm application exits cleanly with proper plugin cleanup
4. Verify fix does not affect Wayland sessions
5. Test that aboutToQuit signal fires correctly for plugin cleanup

fix: 优雅处理X服务器断开连接

当X服务器被终止时（例如从init 3切换到init 5），libX11的默认I/O错误处理器
会调用exit()，绕过Qt的正常关闭流程。这导致插件在全局析构函数中被销毁，此
时对象已部分销毁，从而引发SIGSEGV崩溃。

修改内容：
1. 在CMakeLists.txt中添加X11包依赖，引入Xlib头文件和链接库
2. 实现自定义X I/O错误处理器，调用QCoreApplication::quit()替代exit()
3. 添加SIGPIPE信号处理器，防止X管道断开时崩溃
4. 仅在xcb平台安装处理器，Wayland不需要

这确保插件能收到aboutToQuit信号并正确清理资源。

Log: 通过安装自定义错误处理器修复X服务器断开时的崩溃问题

Influence:
1. 测试X服务器终止时的优雅关闭（init 3到init 5切换）
2. 验证X服务器断开时不会出现SIGSEGV崩溃
3. 确认应用程序能正常退出并正确清理插件
4. 验证修复不影响Wayland会话
5. 测试aboutToQuit信号是否正确触发以清理插件

PMS: BUG-363347
---
 shell/CMakeLists.txt |  2 ++
 shell/main.cpp       | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/shell/CMakeLists.txt b/shell/CMakeLists.txt
index c201baa5b..3d3bc3be2 100644
--- a/shell/CMakeLists.txt
+++ b/shell/CMakeLists.txt
@@ -4,6 +4,7 @@
 
 find_package(Dtk${DTK_VERSION_MAJOR} COMPONENTS Widget REQUIRED)
 find_package(Qt${QT_VERSION_MAJOR} ${REQUIRED_QT_VERSION} REQUIRED COMPONENTS Widgets Gui WaylandClient)
+pkg_check_modules(X11 REQUIRED IMPORTED_TARGET x11)
 find_package(TreelandProtocols REQUIRED)
 pkg_check_modules(WaylandClient REQUIRED IMPORTED_TARGET wayland-client)
 
@@ -46,6 +47,7 @@ target_link_libraries(dde-shell PRIVATE
     Dtk${DTK_VERSION_MAJOR}::Widget
     Qt${QT_VERSION_MAJOR}::DBus
     PkgConfig::WaylandClient
+    PkgConfig::X11
 )
 
 configure_file(${CMAKE_SOURCE_DIR}/misc/dde-shell-plugin@.service.in
diff --git a/shell/main.cpp b/shell/main.cpp
index eebd0069c..f32283d07 100644
--- a/shell/main.cpp
+++ b/shell/main.cpp
@@ -16,6 +16,8 @@
 #include <csignal>
 #include <iostream>
 
+#include <X11/Xlib.h>
+
 #include "applet.h"
 #include "containment.h"
 #include "pluginloader.h"
@@ -46,6 +48,28 @@ static void disableLogOutput()
     QLoggingCategory::setFilterRules("*.debug=false");
 }
 
+// Handle X server disconnection gracefully.
+// When X server is killed (e.g. init 3), libX11's _XDefaultIOError calls exit(),
+// bypassing Qt's normal shutdown. This causes plugins to be destroyed during global
+// destructors when objects are already partially destroyed, leading to SIGSEGV.
+//
+// By installing a custom X I/O error handler, we prevent exit() from being called
+// and instead trigger a clean Qt shutdown via quit(), which fires aboutToQuit
+// and allows plugins to be properly destroyed.
+static int xio_error_handler(Display * /*dpy*/)
+{
+    qCCritical(dsLog) << "X I/O error detected, shutting down gracefully.";
+    QCoreApplication::quit();
+    return 0;
+}
+
+static void sigpipe_handler(int /*sig*/)
+{
+    // 信号处理函数中禁止调用非异步信号安全函数（如 qCCritical），
+    // 否则在持有相关锁时触发信号会导致死锁。
+    QCoreApplication::quit();
+}
+
 class AppletManager
 {
 public:
@@ -218,5 +242,19 @@ int main(int argc, char *argv[])
         manager.quit();
     });
 
+    // Install X11-specific error handlers to prevent exit() from being called
+    // when X server is killed (e.g. during init 3 → init 5 switch).
+    // On Wayland, these are not needed as the error path is different.
+    if (QGuiApplication::platformName().startsWith(QStringLiteral("xcb"))) {
+        XSetIOErrorHandler(xio_error_handler);
+
+        struct sigaction sa;
+        memset(&sa, 0, sizeof(sa));
+        sa.sa_handler = sigpipe_handler;
+        sigemptyset(&sa.sa_mask);
+        sa.sa_flags = 0;
+        sigaction(SIGPIPE, &sa, nullptr);
+    }
+
     return a.exec();
 }