Sources with direct knowledge tell TMZ ... Channing recently volunteered to get tested for COVID-19 after his ex-wife, Jenna Dewan, raised some concerns about him possibly being exposed -- this following a little birthday get-together he hosted in late April.

Some context ... Channing had turned 40 on April 26, and he and five of his closest buddies -- whom we're told were all safely quarantining on their own before rolling through -- hung out for his 40th to do a little dirt biking at his personal ranch. No harm, no foul, right?

Welp, not exactly ... we're told Jenna caught wind and expressed concerns Channing could've been exposed and put their daughter, Everly -- who goes back and forth between mom and dad -- as well as for Jenna herself, at risk. Jenna's also got a new baby at home.

We're told Channing understood the concern and decided to get tested on his own. After a few days of waiting for results -- during which Everly stayed a few extra days with Jenna -- Channing got an answer ... negative.

Our sources say since then, Channing has made up the time he lost ... and the former couple are back on their regular custody schedule, and everything's going off without a hitch. Now, that's how you successfully co-parent!