On Mon, Aug 21, 2017 at 05:46:00PM +0200, Peter Zijlstra wrote: > Now given the above observance rule and the fact that the below report > is from the complete, the thing that happened appears to be: > > > lockdep_map_acquire(&work->lockdep_map) > down_write(&A) > > down_write(&A) > wait_for_completion(&C) > > lockdep_map_acquire(&work_lockdep_map); > complete(&C) > > Which lockdep then puked over because both sides saw the same work > class. > > Byungchul; should we not exclude the work class itself, it appears to me > the workqueue code is explicitly parallel, or am I confused again?
Do you mean the lockdep_map_acquire(&work->lockdep_map) used manuallly? That was introduced by Johannes: commit 4e6045f134784f4b158b3c0f7a282b04bd816887 "workqueue: debug flushing deadlocks with lockdep" I am not sure but, for that purpose, IMHO, we can use a lockdep_map_acquire_read() instead, in process_one_work(), can't we?
