The question is that if you did not take advantage of this previously do you sell now and hope that you can buy back after the 30 day waiting period at the same or a lower price.

If you also have shares in an RSP account one strategy is.

Sell shares of company A in the RRSP.

Sell shares of company B in the NON RRSP.

Buy shares of company B in the RRSP.

Buy shares of company A in the NON RRSP.

You still own the shares but can take the tax loss in the NON RRSP account.