On Wed, 19 Sep 2018, Dmitry Safonov wrote: > On Wed, 2018-09-19 at 16:03 -0400, Mikulas Patocka wrote: > > > > On Wed, 19 Sep 2018, Dmitry Safonov wrote: > > > Thanks much for the testing, Mikulas. > > > Could you try to bisect which of the patches causes it? > > > The most important are 1,2,3 - probably, one of them caused it.. > > > I'll stare a bit into the code. > > > > The patch 3 causes it. > > > > The hangs during reboot take either 80 seconds, 3 minutes or 3:25. > > Thanks much for that again. > Any chance you have sysrq enabled and could print: locks held in system > and kernel backtraces for applications? Stacktrace doesn't work on parisc. It used to work on 4.18, but the kernel 4.19 reportedly requires patched binutils. Mikulas > I suppose, userspace hangs in n_tty_receive_buf_common(), which is > better of cause than null-ptr dereference, but I believe we can improve > it by stopping a reader earlier if there is any writer pending. > > -- > Thanks, > Dmitry >
