Re: [PATCH 6/9] hashmap: Add re-entrancy support to foreach function

Hi Jukka, On 02/12/2015 01:25 AM, Jukka Rissanen wrote: > > On ke, 2015-02-11 at 08:06 -0600, Denis Kenzior wrote: >> >> Hi Patrik, >> > >>> >>> glib also crashed with this pattern. Or usually worked ok, as the >>> removed/added item wasn't always the item used in foreach or the next >>> item. Fixing this to allow any API call successfully work at any time >>> requires quite some more work to be done, the above patch by Jukka was >>> approximately the minimum needed for a remove to work at any one time. >>> >> >> If you find a good way to fix this in the data structure, great. But >> the current fix is not acceptable. We will not be iterating over the >> _entire_ data structure twice. The foreach operation is already >> expensive and too tempting to abuse. > > > The patch would iterate the data structure twice only if user did modify > the hash in the callback func. That is probably not very common case > anyway. > Does not matter. An operation that you expect to take O(n) suddenly becomes O(2n). That's just not acceptable. Remember, we're running on low-power devices, so our data structures will be optimized for speed. Programmer convenience is a secondary concern. Anyway, I pushed a documentation clarification to ell/hashmap.c explaining that the hashmap must be invariant during an ongoing l_hashmap_foreach operation. So you need to find an alternate approach. Think through your data structures carefully.

Regards, -Denis _______________________________________________ ell mailing list ell(a)lists.01.org https://lists.01.org/mailman/listinfo/ell