On Fri, 5 Jan 2018 13:15:45 +0530 "Kohli, Gaurav" <gko...@codeaurora.org> wrote:
> Hi Alan, > >>> > >>> Can you make that code available otherwise it's impossible to see > >>> what the problem might be. > > > > > > https://source.codeaurora.org/quic/la/kernel/msm-4.9/tree/drivers/tty/serial?h=msm-4.9 > As discussed , there not seems a problem as we are getting print > request even when port seems to closed. > > > tty_ldisc_lock(tty, 5 * HZ); > tty_ldisc_setup(tty); > tty_ldisc_unlock(tty) > > But in above lock, there is a chance when flush_to_ldisc will occur > first and acquired a lock in > tty_ldisc_ref itself. Which is fine. If the flush_to_ldisc gets there first then it will find there is a NULL ldisc and do nothing. When it finishes the tty_init_dev will run and will be protected from a further re-entry. If the init_dev gets there first it will complete the init before the flush_to_ldisc is permitted to proceed. In other words we restore the intended invariant that ldisc's do not get entered while their setup routine is running. Alan
