Commit eec9fe7d authored by Ari Entlich's avatar Ari Entlich Committed by Greg Kroah-Hartman
Browse files

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



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: default avatarAri Entlich <atrigent@ccs.neu.edu>
Acked-by: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent d9661adf

drivers/char/vt_ioctl.c

+20 −19
Original line number Diff line number Diff line
@@ -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
@@ -1693,14 +1693,14 @@ 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 {

			/*

			 * The controlling process has died, so we revert back to

			 * normal operation. In this case, we'll also change back
@@ -1711,9 +1711,10 @@ void change_console(struct vc_data *new_vc) 
			 * 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...

		 */

	}

include/linux/vt.h

+2 −1
Original line number Diff line number Diff line
@@ -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 */

CRA Git | Maintained and supported by SUSTech CRA and CCSE