[PATCH v2 2/2] rcu: add uninit destructor for rcu

[Yonggang Luo <luoyonggang@gmail.com>]

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           | 28 ++++++++++++++++++++++++----
 3 files changed, 31 insertions(+), 4 deletions(-)

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..3d5ba695a4 100644
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -234,6 +234,7 @@ retry:
 
 static void *call_rcu_thread(void *opaque)
 {
+    int *rcu_finished_ptr = (int *)opaque;
     struct rcu_head *node;
 
     rcu_register_thread();
@@ -241,6 +242,10 @@ static void *call_rcu_thread(void *opaque)
     for (;;) {
         int tries = 0;
         int n = atomic_read(&rcu_call_count);
+        if (n == 0 && atomic_mb_read(rcu_finished_ptr) == 1)
+        {
+            return NULL;
+        }
 
         /* Heuristically wait for a decent number of callbacks to pile up.
          * Fetch rcu_call_count now, we only must process elements that were
@@ -308,10 +313,12 @@ void rcu_unregister_thread(void)
     qemu_mutex_unlock(&rcu_registry_lock);
 }
 
+static QemuThread rcu_thread;
+static int rcu_finished = 0;
+
 static void rcu_init_complete(void)
 {
-    QemuThread thread;
-
+    atomic_mb_set(&rcu_finished, 0);
     qemu_mutex_init(&rcu_registry_lock);
     qemu_mutex_init(&rcu_sync_lock);
     qemu_event_init(&rcu_gp_event, true);
@@ -321,12 +328,20 @@ static void rcu_init_complete(void)
     /* The caller is assumed to have iothread lock, so the call_rcu thread
      * must have been quiescent even after forking, just recreate it.
      */
-    qemu_thread_create(&thread, "call_rcu", call_rcu_thread,
-                       NULL, QEMU_THREAD_DETACHED);
+    qemu_thread_create(&rcu_thread, "call_rcu", call_rcu_thread,
+                       &rcu_finished, QEMU_THREAD_JOINABLE);
 
     rcu_register_thread();
 }
 
+void rcu_wait_finished(void)
+{
+    if (atomic_xchg(&rcu_finished, 1) == 0)
+    {
+        qemu_thread_join(&rcu_thread);
+    }
+}
+
 static int atfork_depth = 1;
 
 void rcu_enable_atfork(void)
@@ -379,3 +394,8 @@ 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