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-rw-r--r--include/qemu/rcu.h6
-rw-r--r--util/rcu.c20
-rw-r--r--vl.c1
3 files changed, 27 insertions, 0 deletions
diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h
index 83ae2808be..c0da9907e8 100644
--- a/include/qemu/rcu.h
+++ b/include/qemu/rcu.h
@@ -105,6 +105,12 @@ extern void synchronize_rcu(void);
  */
 extern void rcu_register_thread(void);
 extern void rcu_unregister_thread(void);
+
+/*
+ * Support for fork().  fork() support is enabled at startup.
+ */
+extern void rcu_enable_atfork(void);
+extern void rcu_disable_atfork(void);
 extern void rcu_after_fork(void);
 
 struct rcu_head;
diff --git a/util/rcu.c b/util/rcu.c
index 9adc5e4a36..2142ddd93b 100644
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -318,15 +318,35 @@ static void rcu_init_complete(void)
     rcu_register_thread();
 }
 
+static int atfork_depth = 1;
+
+void rcu_enable_atfork(void)
+{
+    atfork_depth++;
+}
+
+void rcu_disable_atfork(void)
+{
+    atfork_depth--;
+}
+
 #ifdef CONFIG_POSIX
 static void rcu_init_lock(void)
 {
+    if (atfork_depth < 1) {
+        return;
+    }
+
     qemu_mutex_lock(&rcu_sync_lock);
     qemu_mutex_lock(&rcu_registry_lock);
 }
 
 static void rcu_init_unlock(void)
 {
+    if (atfork_depth < 1) {
+        return;
+    }
+
     qemu_mutex_unlock(&rcu_registry_lock);
     qemu_mutex_unlock(&rcu_sync_lock);
 }
diff --git a/vl.c b/vl.c
index 99fcfa0442..8967115514 100644
--- a/vl.c
+++ b/vl.c
@@ -4121,6 +4121,7 @@ int main(int argc, char **argv, char **envp)
     set_memory_options(&ram_slots, &maxram_size, machine_class);
 
     os_daemonize();
+    rcu_disable_atfork();
 
     if (pid_file && qemu_create_pidfile(pid_file) != 0) {
         error_report("could not acquire pid file: %s", strerror(errno));