Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=a64314e62d89562b6fc77593648bec3acc35bf61
Commit: a64314e62d89562b6fc77593648bec3acc35bf61
Parent: ed7fdff5d6754f9ef9e47bbf0b171d3d96fb7e41
Author: Jan Lübbe <[EMAIL PROTECTED]>
AuthorDate: Sat Sep 29 18:47:51 2007 +0200
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Sat Sep 29 10:00:15 2007 -0700
fix console change race exposed by CFS
The new behaviour of CFS exposes a race which occurs if a switch is
requested when vt_mode.mode is VT_PROCESS.
The process with vc->vt_pid is signaled before vc->vt_newvt is set.
This causes the switch to fail when triggered by the monitoing process
because the target is still -1.
[ If the signal sending fails, the subsequent "reset_vc(vc)" will then
reset vt_newvt to -1, so this works for that case too. - Linus ]
Signed-off-by: Jan Lübbe <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
drivers/char/vt_ioctl.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c
index c6f6f42..045e688 100644
--- a/drivers/char/vt_ioctl.c
+++ b/drivers/char/vt_ioctl.c
@@ -1208,15 +1208,18 @@ void change_console(struct vc_data *new_vc)
/*
* Send the signal as privileged - kill_pid() will
* tell us if the process has gone or something else
- * is awry
+ * is awry.
+ *
+ * We need to set vt_newvt *before* sending the signal or we
+ * have a race.
*/
+ vc->vt_newvt = new_vc->vc_num;
if (kill_pid(vc->vt_pid, vc->vt_mode.relsig, 1) == 0) {
/*
* It worked. Mark the vt to switch to and
* return. The process needs to send us a
* VT_RELDISP ioctl to complete the switch.
*/
- vc->vt_newvt = new_vc->vc_num;
return;
}
-
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