xen/xenbus: fix self-deadlock after killing user process

[mirror_ubuntu-bionic-kernel.git] / drivers / xen / xenbus / xenbus_dev_frontend.c

diff --git a/drivers/xen/xenbus/xenbus_dev_frontend.c b/drivers/xen/xenbus/xenbus_dev_frontend.c
index 86d702c1ffacf8fae3d70bd3ffae7e014f9dc429..e0c964629c109700f806d9bf7fcd15e344ad1c7d 100644 (file)
--- a/drivers/xen/xenbus/xenbus_dev_frontend.c
+++ b/drivers/xen/xenbus/xenbus_dev_frontend.c
@@ -55,6 +55,7 @@
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/miscdevice.h>
+#include <linux/workqueue.h>
 
 #include <xen/xenbus.h>
 #include <xen/xen.h>
@@ -116,6 +117,8 @@ struct xenbus_file_priv {
        wait_queue_head_t read_waitq;
 
        struct kref kref;
+
+       struct work_struct wq;
 };
 
 /* Read out any raw xenbus messages queued up. */
@@ -300,14 +303,14 @@ static void watch_fired(struct xenbus_watch *watch,
        mutex_unlock(&adap->dev_data->reply_mutex);
 }
 
-static void xenbus_file_free(struct kref *kref)
+static void xenbus_worker(struct work_struct *wq)
 {
        struct xenbus_file_priv *u;
        struct xenbus_transaction_holder *trans, *tmp;
        struct watch_adapter *watch, *tmp_watch;
        struct read_buffer *rb, *tmp_rb;
 
-       u = container_of(kref, struct xenbus_file_priv, kref);
+       u = container_of(wq, struct xenbus_file_priv, wq);
 
        /*
         * No need for locking here because there are no other users,
@@ -333,6 +336,18 @@ static void xenbus_file_free(struct kref *kref)
        kfree(u);
 }
 
+static void xenbus_file_free(struct kref *kref)
+{
+       struct xenbus_file_priv *u;
+
+       /*
+        * We might be called in xenbus_thread().
+        * Use workqueue to avoid deadlock.
+        */
+       u = container_of(kref, struct xenbus_file_priv, kref);
+       schedule_work(&u->wq);
+}
+
 static struct xenbus_transaction_holder *xenbus_get_transaction(
        struct xenbus_file_priv *u, uint32_t tx_id)
 {
@@ -652,6 +667,7 @@ static int xenbus_file_open(struct inode *inode, struct file *filp)
        INIT_LIST_HEAD(&u->watches);
        INIT_LIST_HEAD(&u->read_buffers);
        init_waitqueue_head(&u->read_waitq);
+       INIT_WORK(&u->wq, xenbus_worker);
 
        mutex_init(&u->reply_mutex);
        mutex_init(&u->msgbuffer_mutex);