Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1240774

Re: [PATCH] rbtree: clarify documentation of rbtree_postorder_for_each_entry_safe()

Show all headers | View raw

Hello,

On Sun, Oct 04, 2015 at 06:32:50PM -0400, Cody P Schafer wrote:
> Doing this will cause random nodes to be missed by the iteration because
> rb_erase() may rebalance the tree, changing the ordering that we're
> trying to iterate over.
> 
> The previous documentation for rbtree_postorder_for_each_entry_safe()
> wasn't clear that this wasn't allowed, it was taken from the docs for
> list_for_each_entry_safe(), where erasing isn't a problem due to
> list_del() not reordering.

Ugh... that's a misleading name for an iterator if it doesn't allow
removal of elements during iteration.

> Explicitly warn developers about this potential pit-fall.
> 
> Note that I haven't fixed the actual issue that (it appears) the commit
> referenced above introduced (not familiar enough with that code).
> 
> In general (and in this case), the patterns to follow are:
>  - switch to rb_first() + rb_erase(), don't use
>    rbtree_postorder_for_each_entry_safe().

I'll update it to a while loop on rb_first().

Thanks.

-- 
tejun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

Re: [PATCH] rbtree: clarify documentation of  rbtree_postorder_for_each_entry_safe() Tejun Heo <tj@kernel.org> - 2015-10-06 19:30 +0200

csiph-web