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Date: Tue, 6 Oct 2015 13:25:55 -0400 From: Tejun Heo <tj@...nel.org> To: Cody P Schafer <dev@...yps.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, John de la Garza <john@...ev.com>, Michel Lespinasse <walken@...gle.com>, Peter Zijlstra <peterz@...radead.org>, Rusty Russell <rusty@...tcorp.com.au>, linux-kernel@...r.kernel.org Subject: Re: [PATCH] rbtree: clarify documentation of rbtree_postorder_for_each_entry_safe() 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@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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