[PATCH v4 2/2] rcu: add uninit destructor for rcu

[Yonggang Luo]

This is necessary if the pending  rcu calls are closing and removing
temp files. This also provide a function
void rcu_wait_finished(void);
to fixes test-logging.c test failure on msys2/mingw.
On windows if the file doesn't closed, you can not remove it.

Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>
---
 include/qemu/rcu.h   |  5 +++++
 tests/test-logging.c |  2 ++
 util/rcu.c           | 37 ++++++++++++++++++++++++++++++++++++-
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h
index 570aa603eb..dd0a92c1d0 100644
--- a/include/qemu/rcu.h
+++ b/include/qemu/rcu.h
@@ -124,6 +124,11 @@ extern void rcu_unregister_thread(void);
 extern void rcu_enable_atfork(void);
 extern void rcu_disable_atfork(void);
 
+/*
+ * Wait all rcu call executed and exit the rcu thread.
+ */
+extern void rcu_wait_finished(void);
+
 struct rcu_head;
 typedef void RCUCBFunc(struct rcu_head *head);
 
diff --git a/tests/test-logging.c b/tests/test-logging.c
index 957f6c08cd..7a5b59f4a5 100644
--- a/tests/test-logging.c
+++ b/tests/test-logging.c
@@ -210,6 +210,8 @@ int main(int argc, char **argv)
                          tmp_path, test_logfile_lock);
 
     rc = g_test_run();
+    qemu_log_close();
+    rcu_wait_finished();
 
     rmdir_full(tmp_path);
     g_free(tmp_path);
diff --git a/util/rcu.c b/util/rcu.c
index 60a37f72c3..43367988b9 100644
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -308,10 +308,20 @@ void rcu_unregister_thread(void)
     qemu_mutex_unlock(&rcu_registry_lock);
 }
 
+typedef struct QemuRcuMessage {
+    struct rcu_head rcu;
+    void *message;
+} QemuRcuMessage;
+
+static int rcu_thread_exit_called = 0;
+static int rcu_thread_exited = 0;
+static QemuRcuMessage rcu_thread_message;
+
 static void rcu_init_complete(void)
 {
     QemuThread thread;
-
+    atomic_mb_set(&rcu_thread_exit_called, 0);
+    atomic_mb_set(&rcu_thread_exited, 0);
     qemu_mutex_init(&rcu_registry_lock);
     qemu_mutex_init(&rcu_sync_lock);
     qemu_event_init(&rcu_gp_event, true);
@@ -327,6 +337,26 @@ static void rcu_init_complete(void)
     rcu_register_thread();
 }
 
+static void rcu_thread_exit(QemuRcuMessage *param)
+{
+    atomic_mb_set((int*)param->message, 1);
+    qemu_thread_exit(NULL);
+}
+
+void rcu_wait_finished(void)
+{
+    if (atomic_xchg(&rcu_thread_exit_called, 1) == 0)
+    {
+        rcu_thread_message.message = &rcu_thread_exited;
+        call_rcu(&rcu_thread_message, rcu_thread_exit, rcu);
+    }
+
+    while (atomic_mb_read(&rcu_thread_exited) == 0)
+    {
+        g_usleep(10000);
+    }
+}
+
 static int atfork_depth = 1;
 
 void rcu_enable_atfork(void)
@@ -379,3 +409,8 @@ static void __attribute__((__constructor__)) rcu_init(void)
 #endif
     rcu_init_complete();
 }
+
+static void __attribute__((__destructor__)) rcu_uninit(void)
+{
+    rcu_wait_finished();
+}
-- 
2.28.0.windows.1