On 08/29/2018, 06:28 PM, Dmitry Safonov wrote: > On Wed, 2018-08-29 at 16:46 +0200, Jiri Slaby wrote: >> On 08/29/2018, 04:23 AM, Dmitry Safonov wrote: >>> It's safe to not lock both here - done to silence attempt lockdep >>> assert in >>> tty_ldisc_open(), which will be added with following patch. >> >> SOrry, could you elaborate here? I don't follow... > > Sure, 4/4 patch adds lockdep_assert_held() into tty_ldisc_open(). > Currently ldisc in tty->link isn't locked, which according to code > shouldn't be an issue, as far as I can see. > > So, this patch silences lockdep warining by holding the semaphore, > which is slowpath anyway and doesn't case any new contention.
Eh, no... Adding a lock just to make lockdep happy is a no-go. The locking in tty is already complex enough. > (actually, not holding the semaphore for slave might be an issue if one > opens slave before it's fully initialized, but I'm not sure if it's > possible). If that turns out to be a problem, we can apply the patch. BUt unless it is proven to be so (be it code review or a reproducer), let's leave the locking as it is. thanks, -- js suse labs
