Messages in this thread Patch in this message | | | Date | Thu, 18 Feb 2010 19:48:07 -0500 (EST) | From | atrigent@ccs ... | Subject | [PATCH] 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.
Signed-off-by: Ari Entlich <atrigent@ccs.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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