On Thu, 2016-09-22 at 11:43 +0200, Jan Kara wrote:
> Use assert_spin_locked() macro instead of hand-made BUG_ON statements.
>
> Suggested-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/notify/fanotify/fanotify_user.c | 3 +--
> fs/notify/notification.c | 9 +++------
> 2 files changed, 4 insertions(+), 8 deletions(-)
>
> Andrew, can you please add this cleanup to the fanotify patches you carry?
> Thanks!
>
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 189fab3ac4e6..7ebfca6a1427 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -54,8 +54,7 @@ struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
> static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
> size_t count)
> {
> - BUG_ON(IS_ENABLED(CONFIG_SMP) &&
> - !spin_is_locked(&group->notification_lock));
> + assert_spin_locked(&group->notification_lock);
>
> pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
>
> diff --git a/fs/notify/notification.c b/fs/notify/notification.c
> index 1a8010e7a2a0..66f85c651c52 100644
> --- a/fs/notify/notification.c
> +++ b/fs/notify/notification.c
> @@ -63,8 +63,7 @@ EXPORT_SYMBOL_GPL(fsnotify_get_cookie);
> /* return true if the notify queue is empty, false otherwise */
> bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group)
> {
> - BUG_ON(IS_ENABLED(CONFIG_SMP) &&
> - !spin_is_locked(&group->notification_lock));
> + assert_spin_locked(&group->notification_lock);
> return list_empty(&group->notification_list) ? true : false;
> }
>
> @@ -149,8 +148,7 @@ struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group)
> {
> struct fsnotify_event *event;
>
> - BUG_ON(IS_ENABLED(CONFIG_SMP) &&
> - !spin_is_locked(&group->notification_lock));
> + assert_spin_locked(&group->notification_lock);
>
> pr_debug("%s: group=%p\n", __func__, group);
>
> @@ -172,8 +170,7 @@ struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group)
> */
> struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group)
> {
> - BUG_ON(IS_ENABLED(CONFIG_SMP) &&
> - !spin_is_locked(&group->notification_lock));
> + assert_spin_locked(&group->notification_lock);
>
> return list_first_entry(&group->notification_list,
> struct fsnotify_event, list);
Much cleaner.
That said, I have a personal preference for lockdep_assert_held() in
these situations, which not only tells you whether the lock is locked,
but (I believe) whether it was locked by the current task as well.
Theoretically you could have a different task take this spinlock, and
then call into here without holding it and not get the assertion since
it was locked at the time. Of course, that does require lockdep...
In any case, this is still an improvement:
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
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