radix_tree_tag_get() is not as safe as the docs make out
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From: David Howells on 6 Apr 2010 17:20 Nick Piggin <npiggin(a)suse.de> wrote: > Nack, just drop the BUG_ON. I can do that. > I don't know what you mean by "untrustworthy answer". I was thinking that the answer you get from radix_tree_tag_get() may be invalid if the tag chain is being modified as you read it. So if you do: rcu_read_lock() ... x = radix_tree_tag_get(r, i, t); ... y = radix_tree_tag_get(r, i, t); ... rcu_read_unlock() Then you can't guarantee that x == y, even though you were holding the RCU read lock. As you suggested, I'll try and come up with a comment modification to this effect. David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |