[PATCH v4 9/9] uprobes: shift put_uprobe() from delete_uprobe() to uprobe_unregister()

[Oleg Nesterov <oleg@redhat.com>]

Kill the extra get_uprobe() + put_uprobe() in uprobe_unregister() and
move the possibly final put_uprobe() from delete_uprobe() to its only
caller, uprobe_unregister().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/events/uprobes.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index c06e1a5f1783..f88b7ff20587 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -939,7 +939,6 @@ static void delete_uprobe(struct uprobe *uprobe)
 	rb_erase(&uprobe->rb_node, &uprobes_tree);
 	write_unlock(&uprobes_treelock);
 	RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */
-	put_uprobe(uprobe);
 }
 
 struct map_info {
@@ -1094,7 +1093,6 @@ void uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
 {
 	int err;
 
-	get_uprobe(uprobe);
 	down_write(&uprobe->register_rwsem);
 	if (WARN_ON(!consumer_del(uprobe, uc)))
 		err = -ENOENT;
@@ -1102,10 +1100,16 @@ void uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
 		err = register_for_each_vma(uprobe, NULL);
 
 	/* TODO : cant unregister? schedule a worker thread */
-	if (!err && !uprobe->consumers)
-		delete_uprobe(uprobe);
+	if (!err) {
+		if (!uprobe->consumers)
+			delete_uprobe(uprobe);
+		else
+			err = -EBUSY;
+	}
 	up_write(&uprobe->register_rwsem);
-	put_uprobe(uprobe);
+
+	if (!err)
+		put_uprobe(uprobe);
 }
 EXPORT_SYMBOL_GPL(uprobe_unregister);
 
-- 
2.25.1.362.g51ebf55