> is this an RT-only problem? Because mainline should not allow read->read > locking or read->write locking for reader-writer locks. If this only > happens on v4.18 and not on v4.19 then something must have fixed it. Probably misunderstanding, but I'd say that read->read locking is "the norm"...? If you don't use qrwlock, readers are also "recursive", in part., P0 P1 read_lock(l) write_lock(l) read_lock(l) won't block P0 on the second read_lock(). (qrwlock somehow complicate the analysis; IIUC, they are recursive if and only if in_interrupt().). Andrea > > > Sebastian
