Subject: O2 in C3 plants--photorespiration and photosynthesis

This seems counterintuitive and inefficient to me...

In the Calvin cycle of photosyn., RuBP carboxylase (C3 plants) fixes CO2

to RuBP.  However, a product of the light rxn. of photosynthesis is O2. 

But O2 is also responsible for photorespiration and competes with CO2 

for RuBP carboxylase.  The two 'halves' of photosynthesis seem to be

self-inhibitory or at least seems to be an inefficient process.  O2 from light rxn.

prevents the CO2 fixing in the Dark Rxn.  Am I missing something here? 

Re: O2 in C3 plants--photorespiration and photosynthesis