There is only one caller of check_prev_add() which hands in a zeroed struct stack trace and a function pointer to save_stack(). Inside check_prev_add() the stack_trace struct is checked for being empty, which is always true. Based on that one code path stores a stack trace which is unused. The comment there does not make sense either. It's all leftovers from historical lockdep code (cross release).
Move the variable into check_prev_add() itself and cleanup the nonsensical checks and the pointless stack trace recording. Signed-off-by: Thomas Gleixner <t...@linutronix.de> --- kernel/locking/lockdep.c | 30 ++++++++---------------------- 1 file changed, 8 insertions(+), 22 deletions(-) --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -2158,10 +2158,10 @@ check_deadlock(struct task_struct *curr, */ static int check_prev_add(struct task_struct *curr, struct held_lock *prev, - struct held_lock *next, int distance, struct stack_trace *trace, - int (*save)(struct stack_trace *trace)) + struct held_lock *next, int distance) { struct lock_list *uninitialized_var(target_entry); + struct stack_trace trace; struct lock_list *entry; struct lock_list this; int ret; @@ -2196,17 +2196,8 @@ check_prev_add(struct task_struct *curr, this.class = hlock_class(next); this.parent = NULL; ret = check_noncircular(&this, hlock_class(prev), &target_entry); - if (unlikely(!ret)) { - if (!trace->entries) { - /* - * If @save fails here, the printing might trigger - * a WARN but because of the !nr_entries it should - * not do bad things. - */ - save(trace); - } + if (unlikely(!ret)) return print_circular_bug(&this, target_entry, next, prev); - } else if (unlikely(ret < 0)) return print_bfs_bug(ret); @@ -2253,7 +2244,7 @@ check_prev_add(struct task_struct *curr, return print_bfs_bug(ret); - if (!trace->entries && !save(trace)) + if (!save_trace(&trace)) return 0; /* @@ -2262,14 +2253,14 @@ check_prev_add(struct task_struct *curr, */ ret = add_lock_to_list(hlock_class(next), hlock_class(prev), &hlock_class(prev)->locks_after, - next->acquire_ip, distance, trace); + next->acquire_ip, distance, &trace); if (!ret) return 0; ret = add_lock_to_list(hlock_class(prev), hlock_class(next), &hlock_class(next)->locks_before, - next->acquire_ip, distance, trace); + next->acquire_ip, distance, &trace); if (!ret) return 0; @@ -2287,12 +2278,6 @@ check_prevs_add(struct task_struct *curr { int depth = curr->lockdep_depth; struct held_lock *hlock; - struct stack_trace trace = { - .nr_entries = 0, - .max_entries = 0, - .entries = NULL, - .skip = 0, - }; /* * Debugging checks. @@ -2318,7 +2303,8 @@ check_prevs_add(struct task_struct *curr * added: */ if (hlock->read != 2 && hlock->check) { - int ret = check_prev_add(curr, hlock, next, distance, &trace, save_trace); + int ret = check_prev_add(curr, hlock, next, distance); + if (!ret) return 0; _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu