On 2018-11-23 12:02:55 [+0100], Andrea Parri wrote: > > 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().).
ehm, peterz, is that true? My memory on that is that all readers will block if there is a writer pending. > Andrea Sebastian
