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[PATCH] vt: refactor console SAK processing

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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 <oleg@tv-sign.ru>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Eric W. Biederman 2007-02-10 01:44:34 -08:00 committed by Linus Torvalds
parent 0a7b35cb18
commit 8b6312f4dc
6 changed files with 45 additions and 18 deletions
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12
drivers/char/keyboard.c
View File

@ -595,15 +595,9 @@ static void fn_spawn_con(struct vc_data *vc)
static void fn_SAK(struct vc_data *vc)
{
struct tty_struct *tty = vc->vc_tty;
/*
* SAK should also work in all raw modes and reset
* them properly.
*/
if (tty)
do_SAK(tty);
reset_vc(vc);
struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
PREPARE_WORK(SAK_work, vc_SAK);
schedule_work(SAK_work);
}
static void fn_null(struct vc_data *vc)

6
drivers/char/sysrq.c
View File

@ -88,9 +88,9 @@ static struct sysrq_key_op sysrq_loglevel_op = {
#ifdef CONFIG_VT
static void sysrq_handle_SAK(int key, struct tty_struct *tty)
{
if (tty)
do_SAK(tty);
reset_vc(vc_cons[fg_console].d);
struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
PREPARE_WORK(SAK_work, vc_SAK);
schedule_work(SAK_work);
}
static struct sysrq_key_op sysrq_SAK_op = {
.handler = sysrq_handle_SAK,

13
drivers/char/tty_io.c
View File

@ -3324,10 +3324,8 @@ int tty_ioctl(struct inode * inode, struct file * file,
* Nasty bug: do_SAK is being called in interrupt context. This can
* deadlock. We punt it up to process context. AKPM - 16Mar2001
*/
static void __do_SAK(struct work_struct *work)
void __do_SAK(struct tty_struct *tty)
{
struct tty_struct *tty =
container_of(work, struct tty_struct, SAK_work);
#ifdef TTY_SOFT_SAK
tty_hangup(tty);
#else
@ -3394,6 +3392,13 @@ static void __do_SAK(struct work_struct *work)
#endif
}
static void do_SAK_work(struct work_struct *work)
{
struct tty_struct *tty =
container_of(work, struct tty_struct, SAK_work);
__do_SAK(tty);
}
/*
* The tq handling here is a little racy - tty->SAK_work may already be queued.
* Fortunately we don't need to worry, because if ->SAK_work is already queued,
@ -3404,7 +3409,7 @@ void do_SAK(struct tty_struct *tty)
{
if (!tty)
return;
PREPARE_WORK(&tty->SAK_work, __do_SAK);
PREPARE_WORK(&tty->SAK_work, do_SAK_work);
schedule_work(&tty->SAK_work);
}

28
drivers/char/vt_ioctl.c
View File

@ -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
*/

3
include/linux/console_struct.h
View File

@ -11,6 +11,7 @@
#include <linux/wait.h>
#include <linux/vt.h>
#include <linux/workqueue.h>
struct vt_struct;
@ -103,6 +104,7 @@ struct vc_data {
struct vc {
struct vc_data *d;
struct work_struct SAK_work;
/* might add scrmem, vt_struct, kbd at some time,
to have everything in one place - the disadvantage
@ -110,6 +112,7 @@ struct vc {
};
extern struct vc vc_cons [MAX_NR_CONSOLES];
extern void vc_SAK(struct work_struct *work);
#define CUR_DEF 0
#define CUR_NONE 1

1
include/linux/tty.h
View File

@ -291,6 +291,7 @@ extern void tty_vhangup(struct tty_struct * tty);
extern void tty_unhangup(struct file *filp);
extern int tty_hung_up_p(struct file * filp);
extern void do_SAK(struct tty_struct *tty);
extern void __do_SAK(struct tty_struct *tty);
extern void disassociate_ctty(int priv);
extern void tty_flip_buffer_push(struct tty_struct *tty);
extern speed_t tty_get_baud_rate(struct tty_struct *tty);