[Qemu-devel] [PATCH] Init win32 CRITICAL_SECTION before starting thread; crash when attaching disks

[Bogdan Harjoc]

Git commit 8d3bc51 crashes on win32 on startup because qemu_tcg_init_vcpu
calls:

qemu_thread_create(th, qemu_tcg_cpu_thread_fn, ...
...
qemu_thread_get_handle(th)

which locks th->data->cs, a CRITICAL_SECTION which is initialized only in
the thread_fn, so it finds garbage.

Attached patch initializes it before calling _beginthreadex. GDB/windbg
probably start newly created threads sooner, because this doesn't happen
under a debugger.

With the patch below it boots until it crashes somewhere while attaching
disks (-hda raw_img).

"bt" in gdb only returns "#0  0x00000000 in ??" and generate-core-file
didn't work.

Cheers,

diff -du qemu-8d3bc51\qemu-thread-win32.c
qemu-8d3bc51-new\qemu-thread-win32.c
--- qemu-8d3bc51\qemu-thread-win32.c    Tue Dec 27 17:28:58 2011
+++ qemu-8d3bc51-new\qemu-thread-win32.c    Thu Dec 29 18:59:50 2011
@@ -215,8 +215,6 @@
     if (data->mode == QEMU_THREAD_DETACHED) {
         g_free(data);
         data = NULL;
-    } else {
-        InitializeCriticalSection(&data->cs);
     }
     TlsSetValue(qemu_thread_tls_index, data);
     qemu_thread_exit(start_routine(thread_arg));
@@ -287,6 +285,10 @@
     data->arg = arg;
     data->mode = mode;
     data->exited = false;
+
+    if (data->mode != QEMU_THREAD_DETACHED) {
+        InitializeCriticalSection(&data->cs);
+    }

     hThread = (HANDLE) _beginthreadex(NULL, 0, win32_start_routine,
                                       data, 0, &thread->tid);