net: devlink: introduce "unregistering" mark and use it during devlinks iteration

Add new mark called "unregistering" to be set at the beginning of
devlink_unregister() function. Check this mark during devlinks
iteration in order to prevent getting a reference of devlink which is
being currently unregistered.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/devlink.c b/net/core/devlink.c
index c43c965..6b20196 100644 (file)
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -207,6 +207,7 @@ static const struct nla_policy devlink_selftest_nl_policy[DEVLINK_ATTR_SELFTEST_
 
 static DEFINE_XARRAY_FLAGS(devlinks, XA_FLAGS_ALLOC);
 #define DEVLINK_REGISTERED XA_MARK_1
+#define DEVLINK_UNREGISTERING XA_MARK_2
 
 /* devlink instances are open to the access from the user space after
  * devlink_register() call. Such logical barrier allows us to have certain
@@ -305,6 +306,14 @@ retry:
        devlink = xa_find_fn(&devlinks, indexp, ULONG_MAX, DEVLINK_REGISTERED);
        if (!devlink)
                goto unlock;
+
+       /* In case devlink_unregister() was already called and "unregistering"
+        * mark was set, do not allow to get a devlink reference here.
+        * This prevents live-lock of devlink_unregister() wait for completion.
+        */
+       if (xa_get_mark(&devlinks, *indexp, DEVLINK_UNREGISTERING))
+               goto retry;
+
        /* For a possible retry, the xa_find_after() should be always used */
        xa_find_fn = xa_find_after;
        if (!devlink_try_get(devlink))
@@ -9809,11 +9818,13 @@ void devlink_unregister(struct devlink *devlink)
        ASSERT_DEVLINK_REGISTERED(devlink);
        /* Make sure that we are in .remove() routine */
 
+       xa_set_mark(&devlinks, devlink->index, DEVLINK_UNREGISTERING);
        devlink_put(devlink);
        wait_for_completion(&devlink->comp);
 
        devlink_notify_unregister(devlink);
        xa_clear_mark(&devlinks, devlink->index, DEVLINK_REGISTERED);
+       xa_clear_mark(&devlinks, devlink->index, DEVLINK_UNREGISTERING);
 }
 EXPORT_SYMBOL_GPL(devlink_unregister);