On Thu, Mar 24, 2016 at 12:21:04AM +0000, Esquivel, Randall Jose wrote:
> Hello,
>
> I have been looking at the code used to update the weak references in OVS
> and would like to clarify what is the correct usage of the function
> assess_weak_refs().
> This function is called inside for_each_txn_row():
> ...
> while (t->n_processed < hmap_count(&t->txn_rows)) {
> ...
> assess_weak_refs() <- callback
> ...
>
> The function for_each_txn_row() iterates internally calling on each cycle to
> assess_weak_refs() controlled by the counter
>
> hmap_count(&t->txn_rows)
>
> This counter represents the number of nodes currently in 'hmap'. This counter
> is incremented each time a row is processed inside assess_weak_refs() for rows
> deleted or modified in the original code. The call hierarchy used to update
> the
> hmap is shown:
>
> ovsdb_txn_row_modify()
> ovsdb_txn_row_create()
> hmap_insert()
> hmap_insert_at()
> hmap_insert_fast()
> ...
> hmap->n++;
>
> What the code is apparently doing...
>
> 1. In the case a row has been deleted assess_weak_refs() enters and
> modify the rows with references to the row that has been deleted and exit.
> These rows are now in the hmap.
> 2. For each of the modified rows (which have weak references to the
> deleted row),
> a. Run assess_weak_refs() and modify rows that have weak references to
> this row. [dst_refs are the weak references to current row] ***
> i. ovsdb_table_get_row()
> checks for rows in the hmap matching a uuid and if the row exists a weak
> reference is added.
>
> The implementation modifies the rows with weak references using:
>
> if (txn_row->old) {
> ...
> LIST_FOR_EACH_SAFE (weak, next, dst_node, &txn_row->old->dst_refs) {
> ...
>
> but it evaluates deleted or modified rows.
>
> ***When a row has been deleted, the rows with weak references (*) to it get
> modified
> and its weak references updated. But this produces that the rows with weak
> references
> to the rows in (*) get also updated, and so on.
>
> Could the weak references be updated after modifying *only* the rows with
> weak
> references to the deleted row, or is it required that all dependent rows get
> updated?
I think that the former is true.
> Is this the expected behavior of this function?
Is what the expected behavior of this function?
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