Re: Please help reviewing ! Got another crash because of the ttymodem() / ttyclose() race

On Friday 30 June 2006 05:09, Martin Blapp wrote:
> 
> Hi all,
> 
> This time its FreeBSD 5.5 RELEASE. Same code is in 6.X (which crashed on a 
> different server 5 days ago) and CURRENT.
> 
> #25 0xc064f4bd in ttymodem ()
> #26 0xc06532bd in ptcclose ()
> #27 0xc05e4e14 in spec_close ()
> #28 0xc05e3edf in spec_vnoperate ()
> #29 0xc06815e0 in vn_close ()
> #30 0xc06825f2 in vn_closefile ()
> #31 0xc0601ba4 in fdrop_locked ()
> #32 0xc0601af1 in fdrop ()
> #33 0xc060015b in closef ()
> #34 0xc05fd5e5 in close ()
> #35 0xc07c5e97 in syscall ()
> 
> Can PLEASE PLEASE someone help me fix this problem
> and review the patch ?
> 
> The patch is based on Max Laiers tty.t_pgrp patch.
> 
> http://mx.imp.ch/patch-tty.t_pgrp.diff
> 
> Especially the part in ttyinfo() needs to be reviewed
> carefully.

I'm not sure that the proctree_lock should protect t_pgrp as that is part
of the tty structure, not process groups or session structures.  I think
probably it should be protected by Giant for now until the tty subsystem
is locked.  Also, the ttyinfo() part will not work since it tries to
acquire a mutex (PGRP_LOCK()) while holding a spin mutex (sched_lock).

-- 
John Baldwin