kprobes: No need to unlock kprobe_insn_mutex

Remove needless kprobe_insn_mutex unlocking during safety check
in garbage collection, because if someone releases a dirty slot
during safety check (which ensures other cpus doesn't execute
all dirty slots), the safety check must be fail. So, we need to
hold the mutex while checking safety.

Signed-off-by: Masami Hiramatsu <[email protected]>
Cc: Ananth N Mavinakayanahalli <[email protected]>
Cc: Jim Keniston <[email protected]>
Cc: Ananth N Mavinakayanahalli <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

Author: Masami Hiramatsu

kernel/kprobes.c

@@ -237,13 +237,9 @@ static int __kprobes collect_garbage_slots(void)
 {
 	struct kprobe_insn_page *kip;
 	struct hlist_node *pos, *next;
-	int safety;
 
 	/* Ensure no-one is preepmted on the garbages */
-	mutex_unlock(&kprobe_insn_mutex);
-	safety = check_safety();
-	mutex_lock(&kprobe_insn_mutex);
-	if (safety != 0)
+	if (check_safety())
 		return -EAGAIN;
 
 	hlist_for_each_entry_safe(kip, pos, next, &kprobe_insn_pages, hlist) {