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tty: Add a new VT mode which is like VT_PROCESS but doesn't require a VT_RELDISP ioctl call

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This new VT mode (VT_PROCESS_AUTO) does everything that VT_PROCESS does
except that it doesn't wait for a VT_RELDISP ioctl before switching
away from a VT with that mode.

If the X server eventually uses this new mode, debugging and crash
recovery should become easier. This is because even when currently in
the VT of a frozen X server it would still be possible to switch out
by doing SysRq-r and then CTRL-<number of a text vt>, sshing in and
doing chvt <number of a text vt>, or any other method of VT switching.
The general concensus on #xorg-devel seems to be that it should be
safe to use this with X now that we have KMS.

This also moves the VT_ACKACQ define to a more appropriate place,
for clarity's sake.

Signed-off-by: Ari Entlich <atrigent@ccs.neu.edu>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Ari Entlich 2010-02-19 09:37:55 -05:00 committed by Greg Kroah-Hartman
parent d9661adfb8
commit eec9fe7d1a
2 changed files with 22 additions and 20 deletions
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39
drivers/char/vt_ioctl.c
View file

@ -888,7 +888,7 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
ret = -EFAULT;
goto out;
}
if (tmp.mode != VT_AUTO && tmp.mode != VT_PROCESS) {
if (tmp.mode != VT_AUTO && tmp.mode != VT_PROCESS && tmp.mode != VT_PROCESS_AUTO) {
ret = -EINVAL;
goto out;
}
@ -1622,7 +1622,7 @@ static void complete_change_console(struct vc_data *vc)
* telling it that it has acquired. Also check if it has died and
* clean up (similar to logic employed in change_console())
*/
if (vc->vt_mode.mode == VT_PROCESS) {
if (vc->vt_mode.mode == VT_PROCESS || vc->vt_mode.mode == VT_PROCESS_AUTO) {
/*
* Send the signal as privileged - kill_pid() will
* tell us if the process has gone or something else
@ -1682,7 +1682,7 @@ void change_console(struct vc_data *new_vc)
* vt to auto control.
*/
vc = vc_cons[fg_console].d;
if (vc->vt_mode.mode == VT_PROCESS) {
if (vc->vt_mode.mode == VT_PROCESS || vc->vt_mode.mode == VT_PROCESS_AUTO) {
/*
* Send the signal as privileged - kill_pid() will
* tell us if the process has gone or something else
@ -1693,27 +1693,28 @@ void change_console(struct vc_data *new_vc)
*/
vc->vt_newvt = new_vc->vc_num;
if (kill_pid(vc->vt_pid, vc->vt_mode.relsig, 1) == 0) {
if(vc->vt_mode.mode == VT_PROCESS)
/*
* It worked. Mark the vt to switch to and
* return. The process needs to send us a
* VT_RELDISP ioctl to complete the switch.
*/
return;
} else {
/*
* It worked. Mark the vt to switch to and
* return. The process needs to send us a
* VT_RELDISP ioctl to complete the switch.
* The controlling process has died, so we revert back to
* normal operation. In this case, we'll also change back
* to KD_TEXT mode. I'm not sure if this is strictly correct
* but it saves the agony when the X server dies and the screen
* remains blanked due to KD_GRAPHICS! It would be nice to do
* this outside of VT_PROCESS but there is no single process
* to account for and tracking tty count may be undesirable.
*/
return;
reset_vc(vc);
}
/*
* The controlling process has died, so we revert back to
* normal operation. In this case, we'll also change back
* to KD_TEXT mode. I'm not sure if this is strictly correct
* but it saves the agony when the X server dies and the screen
* remains blanked due to KD_GRAPHICS! It would be nice to do
* this outside of VT_PROCESS but there is no single process
* to account for and tracking tty count may be undesirable.
*/
reset_vc(vc);
/*
* Fall through to normal (VT_AUTO) handling of the switch...
* Fall through to normal (VT_AUTO and VT_PROCESS_AUTO) handling of the switch...
*/
}

3
include/linux/vt.h
View file

@ -27,7 +27,7 @@ struct vt_mode {
#define VT_SETMODE 0x5602 /* set mode of active vt */
#define VT_AUTO 0x00 /* auto vt switching */
#define VT_PROCESS 0x01 /* process controls switching */
#define VT_ACKACQ 0x02 /* acknowledge switch */
#define VT_PROCESS_AUTO 0x02 /* process is notified of switching */
struct vt_stat {
unsigned short v_active; /* active vt */
@ -38,6 +38,7 @@ struct vt_stat {
#define VT_SENDSIG 0x5604 /* signal to send to bitmask of vts */
#define VT_RELDISP 0x5605 /* release display */
#define VT_ACKACQ 0x02 /* acknowledge switch */
#define VT_ACTIVATE 0x5606 /* make vt active */
#define VT_WAITACTIVE 0x5607 /* wait for vt active */