+Peter On Thu, Mar 23, 2017 at 4:22 PM, <l...@pengaru.com> wrote: > On Thu, Mar 23, 2017 at 11:57:22AM -0500, Rob Herring wrote: >> On Thu, Mar 23, 2017 at 08:46:03AM -0500, Rob Herring wrote: >> > On Thu, Mar 23, 2017 at 12:30:18AM -0700, l...@pengaru.com wrote: >> > > On Wed, Mar 22, 2017 at 11:44:18PM -0700, l...@pengaru.com wrote: >> > > > On Wed, Mar 22, 2017 at 07:08:46PM -0700, l...@pengaru.com wrote: >> > > > > Hello list, >> > > > > >> > > > > After approximately one day day of running 4.11.0-rc3 with 7e54d9d >> > > > > reverted to >> > > > > enable regular use, this happened upon destroying an xterm: >> > > > > >> >> [...] >> >> > > > >> > > > Added Rob Herring, author of c3485ee to CC list. >> > > > >> > > >> > > I suspect this part was a mistake: >> > > >> > > - tty = READ_ONCE(port->itty); >> > > - if (tty == NULL) >> > > - return; >> > > >> > > Note release_tty() tty->port->itty is assigned NULL before calling >> > > tty_buffer_cancel_work(): >> > >> > The READ_ONCE should still handle that. >> > >> > Anyway, the changes were purely to try to remove the need for a ldisc in >> > the serdev case and avoid referencing it. In fact we still have an >> > ldisc, it's just not used. So we can restore the original ordering. >> > >> > Can you try this patch: >> > >> >> Please try this one instead. It passes the tty struct around instead of >> the ldisc. >> > > Happy to test the fix, except reproducing the bug without changing anything > at all has proven elusive. AFAIK we just have my single experience > described in the report, I'm unconfident in my ability to validate any > fixes for this specific bug. > > If you think you understand the root cause, maybe you can conceive of a > more reliable reproducer than me just using my machine? It appears I may > have just been very (un)lucky.
Honestly, I don't understand why my change caused a problem. The fix just changes things back to how things we ordered before. Looks like the need for READ_ONCE was originally found with ktsan, so maybe it could help here. But I've never used it. Rob
