On Tue, Nov 06, 2018 at 08:51:54PM +0000, Jason Gunthorpe wrote: > On Tue, Nov 06, 2018 at 12:34:11PM -0800, Daniel Jordan wrote: > > > > What isn't clear is if this calling thread is waiting or not. Only do > > > this inheritance trick if it is actually waiting on the work. If it is > > > not, nobody cares. > > > > The calling thread waits. Even if it didn't though, the inheritance trick > > would still be desirable for timely completion of the job. > > Can you make lockdep aware that this is synchronous? > > ie if I do > > mutex_lock() > ktask_run() > mutex_lock() > > Can lockdep know that all the workers are running under that lock? > > I'm thinking particularly about rtnl_lock as a possible case, but > there could also make some sense to hold the read side of the mm_sem > or similar like the above. Yes, the normal trick is adding a fake lock to ktask_run and holding that over the actual job. See lock_map* in flush_workqueue() vs process_one_work().
