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Message-ID: <2582583.137891266540487930.JavaMail.root@zimbra>
Date: Thu, 18 Feb 2010 19:48:07 -0500 (EST)
From: atrigent@....neu.edu
To: linux-kernel@...r.kernel.org
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] 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.
Signed-off-by: Ari Entlich <atrigent@....neu.edu>
---
This should apply to Linus' tree. It has been compile tested only - I just
want to see whether I'm on the right track/whether there's anything big I
overlooked/whether there are any obvious mistakes here.
I was advised to CC Linus and akpm because of the subsystem that this
touches. I hope that was appropriate.
Thanks!
drivers/char/vt_ioctl.c | 39 ++++++++++++++++++++-------------------
include/linux/vt.h | 1 +
2 files changed, 21 insertions(+), 19 deletions(-)
diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c
index 6aa1028..87778dc 100644
--- a/drivers/char/vt_ioctl.c
+++ b/drivers/char/vt_ioctl.c
@@ -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...
*/
}
diff --git a/include/linux/vt.h b/include/linux/vt.h
index d5dd0bc..dedf419 100644
--- a/include/linux/vt.h
+++ b/include/linux/vt.h
@@ -27,6 +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_PROCESS_AUTO 0x02 /* process is notified of switching */
#define VT_ACKACQ 0x02 /* acknowledge switch */
struct vt_stat {
--
1.6.4.4
--
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