Re: [PATCH 1/9] libtraceeval: Add check for updates to know to recreate iter array

[Ross Zwisler <zwisler@google.com>]

On Thu, Aug 17, 2023 at 06:24:14PM -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
> 
> When an iterator is created, it creates an array of pointers to point to
> all the elements in the traceeval. This is used to index through the
> entities in an nice order. But if an event is added or removed from the
> traceeval, the size and count of this array will be off in the iterator.
> 
> Add an "update_counter" that gets incremented every time an item is added
> or removed (doesn't need to keep track of updates to existing entries). If
> the counter is different from the last time the iterator created the sort
> array, it will need to delete and recreate the list again before it can do
> a sort.
> 
> Note: It is safe to use the iterator to remove times, so a removal (or
                                                 items
> even insert) should not affect the traceeval_iterator_next(). But it
> should be explained in the man pages (soon to be written) that doing so
> must be done with care. And maybe a helper function should be used
> instead!
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>  src/eval-local.h |  2 ++
>  src/histograms.c | 91 ++++++++++++++++++++++++++++++++++++++----------
>  2 files changed, 74 insertions(+), 19 deletions(-)
<>
> @@ -1168,6 +1190,31 @@ static int iter_cmp(const void *A, const void *B, void *data)
>  	return 0;
>  }
>  
> +static int check_update(struct traceeval_iterator *iter)
> +{
> +	struct entry **entries;
> +	size_t nr_entries;
> +	int ret;
> +
> +	/* Was something added or removed from the teval? */
> +	if (iter->teval->update_counter == iter->update_counter)
> +		return 0;
> +
> +	entries = iter->entries;
> +	nr_entries = iter->nr_entries;
> +
> +	/* Something changed, need to recreate the array */
> +	ret = create_iter_array(iter);
> +	if (ret < 0) {
> +		iter->entries = entries;
> +		iter->nr_entries = nr_entries;
> +			return -1;

                ^^ extra tab

Aside from these 2 nits:

Reviewed-by: Ross Zwisler <zwisler@google.com>