[PATCH] linux-user: un-register threads from RCU before exit

["Alex Bennée" <alex.bennee@linaro.org>]

Through a mechanism I don't quite yet understand we can find ourselves
with a left over RCU thread when we exit group. This is a racy failure
that occurs for example with:

  alpha-linux-user running testthread
    with libhowvec.so plugin
    but only when run from make

This may not be the correct fix but it seems to alleviate the
symptoms.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
---
 linux-user/exit.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/linux-user/exit.c b/linux-user/exit.c
index a362ef67d2c..1c7ce347324 100644
--- a/linux-user/exit.c
+++ b/linux-user/exit.c
@@ -28,12 +28,13 @@ extern void __gcov_dump(void);
 
 void preexit_cleanup(CPUArchState *env, int code)
 {
+    rcu_unregister_thread();
 #ifdef TARGET_GPROF
-        _mcleanup();
+    _mcleanup();
 #endif
 #ifdef CONFIG_GCOV
-        __gcov_dump();
+    __gcov_dump();
 #endif
-        gdb_exit(env, code);
-        qemu_plugin_atexit_cb();
+    gdb_exit(env, code);
+    qemu_plugin_atexit_cb();
 }
-- 
2.20.1