oslib-posix: take lock before qemu_cond_broadcast

In touch_all_pages, if the mutex is not taken around qemu_cond_broadcast,
qemu_cond_broadcast may be called before all touch page threads enter
qemu_cond_wait. In this case, the touch page threads wait forever for the
main thread to wake them up, causing a deadlock.

Signed-off-by: Bauerchen <bauerchen@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

util/oslib-posix.c

@@ -492,8 +492,11 @@ static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages,
                            QEMU_THREAD_JOINABLE);
         addr += memset_thread[i].numpages * hpagesize;
     }
+
+    qemu_mutex_lock(&page_mutex);
     threads_created_flag = true;
     qemu_cond_broadcast(&page_cond);
+    qemu_mutex_unlock(&page_mutex);
 
     for (i = 0; i < memset_num_threads; i++) {
         qemu_thread_join(&memset_thread[i].pgthread);