Second naive question about map operation

[Jonathan S. Shapiro]

A second naive question.

Imagine that thread A performs separate map operations to each of B and
C (maps of the same thing). This results in a dependency relationship of
the form:

     A
    / \
   B   C

Given that these operations have happened, is there a way for A to
revoke the mapping held by B without also revoking the mapping held by
C?

Does it matter?
-- 
Jonathan S. Shapiro <shap at eros-os.org>