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weston-launch: reset tty properly 

On weston-launch exit we see errors such as:
  failed to restore keyboard mode: Invalid argument
  failed to set KD_TEXT mode on tty: Invalid argument

This has been resolved by making sure the tty file descriptor
does not get closed. However, the ioctrl's KDSKBMODE/KDSETMODE
and VT_SETMODE still fail with -EIO:
  failed to restore keyboard mode: Input/output error
  failed to set KD_TEXT mode on tty: Input/output error

It turns out the reason for this lies in some very particular
behavior of the kernel, the separation of weston-launch/weston
and the fact that we restore the tty only after the weston
process quits: When the controlling process for a TTY exits,
all open file descriptors for that TTY are put in a hung-up
state! For more details see this systemd-logind issue:
https://github.com/systemd/systemd/issues/989

We can work around by reopening the particular TTY. This allows
to properly restore the TTY settings such that a successive VT
switch will show text terminals fine again.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
This commit is contained in:
Stefan Agner 2019-11-14 23:39:40 +01:00 committed by Pekka Paalanen
parent 247392a322
commit bd1e39a787
1 changed files with 14 additions and 0 deletions
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14
libweston/weston-launch.c
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@ -440,6 +440,7 @@ quit(struct weston_launch *wl, int status)
{
struct vt_mode mode = { 0 };
int err;
int oldtty;
close(wl->signalfd);
close(wl->sock[0]);
@ -452,6 +453,19 @@ quit(struct weston_launch *wl, int status)
pam_end(wl->ph, err);
}
/*
* Get a fresh handle to the tty as the previous one is in
* hang-up state since weston (the controlling process for
* the tty) exit at this point. Reopen before closing the
* file descriptor to avoid a potential race condition.
*
* A similar fix exists in logind, see:
* https://github.com/systemd/systemd/pull/990
*/
oldtty = wl->tty;
wl->tty = open_tty_by_number(wl->ttynr);
close(oldtty);
if (ioctl(wl->tty, KDSKBMUTE, 0) &&
ioctl(wl->tty, KDSKBMODE, wl->kb_mode))
fprintf(stderr, "failed to restore keyboard mode: %s\n",