On Sun, 2 Jun 2024 22:06:13 -0400 Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > +/* Make @ops trace evenything except what all its subops do not trace */ > > > +static struct ftrace_hash *intersect_hashes(struct ftrace_ops *ops) > > > +{ > > > + struct ftrace_hash *new_hash = NULL; > > > + struct ftrace_ops *subops; > > > + int size_bits; > > > + int ret; > > > + > > > + list_for_each_entry(subops, &ops->subop_list, list) { > > > + struct ftrace_hash *next_hash; > > > + > > > + if (!new_hash) { > > > + size_bits = subops->func_hash->notrace_hash->size_bits; > > > + new_hash = alloc_and_copy_ftrace_hash(size_bits, ops->func_hash->notrace_hash); > > > + if (!new_hash) > > > + return NULL; > > > > If the first subops has EMPTY_HASH, this allocates small empty hash (!= EMPTY_HASH) > > on `new_hash`. > > Could we just change the above to be: ? > > new_hash = ftrace_hash_empty(ops->func_hash->notrace_hash) ? EMPTY_HASH : > alloc_and_copy_ftrace_hash(size_bits, ops->func_hash->notrace_hash); > if (!new_hash) > return NULL; Yeah, and if new_hash is EMPTY_HASH, we don't need looping on the rest of the hashes, right? > > > > > > > + continue; > > > + } > > > + size_bits = new_hash->size_bits; > > > + next_hash = new_hash; > > > > And it is assigned to `next_hash`. > > > > > + new_hash = alloc_ftrace_hash(size_bits); > > > + ret = intersect_hash(&new_hash, next_hash, subops->func_hash->notrace_hash); > > > > Since the `next_hash` != EMPTY_HASH but it is empty, this keeps `new_hash` > > empty but allocated. > > > > > + free_ftrace_hash(next_hash); > > > + if (ret < 0) { > > > + free_ftrace_hash(new_hash); > > > + return NULL; > > > + } > > > + /* Nothing more to do if new_hash is empty */ > > > + if (new_hash == EMPTY_HASH) > > > > Since `new_hash` is empty but != EMPTY_HASH, this does not pass. Keep looping on. > > > > > + break; > > > + } > > > + return new_hash; > > > > And this will return empty but not EMPTY_HASH hash. > > > > > > So, we need; > > > > #define FTRACE_EMPTY_HASH_OR_NULL(hash) (!(hash) || (hash) == EMPTY_HASH) > > > > if (FTRACE_EMPTY_HASH_OR_NULL(subops->func_hash->notrace_hash)) { > > free_ftrace_hash(new_hash); > > new_hash = EMPTY_HASH; > > break; > > } > > > > at the beginning of the loop. > > Also, at the end of the loop, > > > > if (ftrace_hash_empty(new_hash)) { > > free_ftrace_hash(new_hash); > > new_hash = EMPTY_HASH; > > break; > > } And we still need this (I think this should be done in intersect_hash(), we just need to count the number of entries.) > > > > > +} > > > + > > > +/* Returns 0 on equal or non-zero on non-equal */ > > > +static int compare_ops(struct ftrace_hash *A, struct ftrace_hash *B) > > > > nit: Isn't it better to be `bool hash_equal()` and return true if A == B ? > > Sure. I guess I was thinking too much of strcmp() logic :-p Yeah, it's the curse of the C programmer :( (even it is good for sorting.) Thank you, > > > > > Thank you, > > Thanks for the review. > > -- Steve > > > > > > +{ > > > + struct ftrace_func_entry *entry; > > > + int size; > > > + int i; > > > + > > > + if (!A || A == EMPTY_HASH) > > > + return !(!B || B == EMPTY_HASH); > > > + > > > + if (!B || B == EMPTY_HASH) > > > + return !(!A || A == EMPTY_HASH); > > > + > > > + if (A->count != B->count) > > > + return 1; > > > + > > > + size = 1 << A->size_bits; > > > + for (i = 0; i < size; i++) { > > > + hlist_for_each_entry(entry, &A->buckets[i], hlist) { > > > + if (!__ftrace_lookup_ip(B, entry->ip)) > > > + return 1; > > > + } > > > + } > > > + > > > + return 0; > > > +} > > > + > > > > > -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>