On Wed, 24 Oct 2001, Jonathan Lemon wrote: > Hmm. The way the revamped console code works is this: > > cn_devopen() calls vn_open() to open the device. If this is not a > VCHR device, then it is closed. Otherwise, the vnode is stashed in > cnd->cnd_vp. > > When the device is closed though cnclose(), it walks through a list > of console devices, and if cnd_vp != NULL, calls vn_close() for that > vnode, and then NULLs out cnd_vp. (drops the reference.) > > My understanding is that vn_open/vn_close will track the count of > outstanding references to the vnode, so this should be safe to do.
The reference counts were inadequate for handling controlling terminals in the old version. I don't see how this can work now. You do extra opens. This will prevent controlling ttys going away properly. E.g., suppose sio0 is a console device and is completely closed. The following sequence of operations should leave it a non-controlling tty: sio0's ref count open sio0 1 make sio0 a ctty 2 open cn 3 close sio0 2 lose sio0 as a ctty 1 sioclose() will not be called here since the reference count is > 0, so ctty-related stuff in its tty struct will not be cleared, and things break. Similarly with sio0 and cn reversed. The old code had kludges to handle one of these cases. I had fixes for the other one. These are now invalid (sigh). I didn't commit them because there seemed to be a lot of races nearby. Perhaps the panic is caused a race. The races are related to stashing of pointers related to controlling terminals. The lifetime of these pointers is unclear. Bruce To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message