K 10
svn:author
V 8
hselasky
K 8
svn:date
V 27
2020-05-22T08:59:12.963610Z
K 7
svn:log
V 564
MFC r361075:
Assign process group of the TTY under the "proctree_lock".

This fixes a race where concurrent calls to doenterpgrp() and
leavepgrp() while TIOCSCTTY is executing may result in tp->t_pgrp
changing value so that tty_rel_pgrp() misses clearing it to NULL. For
more details refer to the use of pgdelete() in the kernel.

No functional change intended.

Panic backtrace:
__mtx_lock_sleep() # page fault due to using destroyed mutex
tty_signal_pgrp()
tty_ioctl()
ptsdev_ioctl()
kern_ioctl()
sys_ioctl()
amd64_syscall()

Sponsored by:	Mellanox Technologies

END