I agree with comment that this is NOT an inservice. If everyone is truly applying the term properly, an inservice should be a learning experience. Whether or not you are being taught something you don't know already can vary. But, in my experience, management views inservice meetings as learning experiences and doesn not want them to 'degenerate' into gripe sessions.
But if you want to discuss specific job concerns, then yes, a separate team meeting (or 'bitch session') is needed.