regression with TTY changes in v5.12-rc1

[Pierre-Louis Bossart]

Hi,
Our SOF/audio CI shows an across-the-board regression when we try 
v5.12-rc1, specifically on pause/resume tests with an interactive 
terminal running 'aplay -i' commands managed by expect to simulate the 
user pressing the space bar to pause/unpause. It turns out the processes 
are not longer killed and the audio devices remain busy (see publicly 
available test results listed below).

git bisect points to commit 33d4ae9885987 ("drivers:tty:pty: Fix a race
causing data loss on close"). Reverting the patch fixes the issue on all 
test devices.

Further analysis with Corey Minyard points to a problem where a slave 
tty will not get a SIGHUP when the master is closed.

Unless there is an alternate fix, a revert looks necessary?

Regards
-Pierre

https://github.com/thesofproject/linux/pull/2772
https://sof-ci.01.org/linuxpr/PR2772/build5352/devicetest/