From 8b6312f4dcc1efe7975731b6c47dd134282bd9ac Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Sat, 10 Feb 2007 01:44:34 -0800 Subject: [PATCH] vt: refactor console SAK processing This does several things. - It moves looking up of the current foreground console into process context where we can safely take the semaphore that protects this operation. - It uses the new flavor of work queue processing. - This generates a factor of do_SAK, __do_SAK that runs immediately. - This calls __do_SAK with the console semaphore held ensuring nothing else happens to the console while we process the SAK operation. - With the console SAK processing moved into process context this patch removes the xchg operations that I used to attempt to attomically update struct pid, because of the strange locking used in the SAK processing. With SAK using the normal console semaphore nothing special is needed. Cc: Oleg Nesterov Signed-off-by: Eric W. Biederman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/char/vt_ioctl.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) (limited to 'drivers/char/vt_ioctl.c') diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c index dc8368ebb1a..3a5d301e783 100644 --- a/drivers/char/vt_ioctl.c +++ b/drivers/char/vt_ioctl.c @@ -672,7 +672,8 @@ int vt_ioctl(struct tty_struct *tty, struct file * file, vc->vt_mode = tmp; /* the frsig is ignored, so we set it to 0 */ vc->vt_mode.frsig = 0; - put_pid(xchg(&vc->vt_pid, get_pid(task_pid(current)))); + put_pid(vc->vt_pid); + vc->vt_pid = get_pid(task_pid(current)); /* no switch is required -- saw@shade.msu.ru */ vc->vt_newvt = -1; release_console_sem(); @@ -1063,12 +1064,35 @@ void reset_vc(struct vc_data *vc) vc->vt_mode.relsig = 0; vc->vt_mode.acqsig = 0; vc->vt_mode.frsig = 0; - put_pid(xchg(&vc->vt_pid, NULL)); + put_pid(vc->vt_pid); + vc->vt_pid = NULL; vc->vt_newvt = -1; if (!in_interrupt()) /* Via keyboard.c:SAK() - akpm */ reset_palette(vc); } +void vc_SAK(struct work_struct *work) +{ + struct vc *vc_con = + container_of(work, struct vc, SAK_work); + struct vc_data *vc; + struct tty_struct *tty; + + acquire_console_sem(); + vc = vc_con->d; + if (vc) { + tty = vc->vc_tty; + /* + * SAK should also work in all raw modes and reset + * them properly. + */ + if (tty) + __do_SAK(tty); + reset_vc(vc); + } + release_console_sem(); +} + /* * Performs the back end of a vt switch */ -- cgit v1.2.3