The patch titled
vt: refactor console SAK processing
has been added to the -mm tree. Its filename is
vt-refactor-console-sak-processing.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: vt: refactor console SAK processing
From: ebiederm@xxxxxxxxxxxx (Eric W. Biederman)
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@xxxxxxxxxx>
Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
drivers/char/keyboard.c | 12 +++---------
drivers/char/sysrq.c | 6 +++---
drivers/char/tty_io.c | 13 +++++++++----
drivers/char/vt_ioctl.c | 28 ++++++++++++++++++++++++++--
include/linux/console_struct.h | 3 +++
include/linux/tty.h | 1 +
6 files changed, 45 insertions(+), 18 deletions(-)
diff -puN drivers/char/keyboard.c~vt-refactor-console-sak-processing drivers/char/keyboard.c
--- a/drivers/char/keyboard.c~vt-refactor-console-sak-processing
+++ a/drivers/char/keyboard.c
@@ -595,15 +595,9 @@ static void fn_spawn_con(struct vc_data
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)
diff -puN drivers/char/sysrq.c~vt-refactor-console-sak-processing drivers/char/sysrq.c
--- a/drivers/char/sysrq.c~vt-refactor-console-sak-processing
+++ a/drivers/char/sysrq.c
@@ -88,9 +88,9 @@ static struct sysrq_key_op sysrq_logleve
#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,
diff -puN drivers/char/tty_io.c~vt-refactor-console-sak-processing drivers/char/tty_io.c
--- a/drivers/char/tty_io.c~vt-refactor-console-sak-processing
+++ a/drivers/char/tty_io.c
@@ -3324,10 +3324,8 @@ int tty_ioctl(struct inode * inode, stru
* 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
#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);
}
diff -puN drivers/char/vt_ioctl.c~vt-refactor-console-sak-processing drivers/char/vt_ioctl.c
--- a/drivers/char/vt_ioctl.c~vt-refactor-console-sak-processing
+++ a/drivers/char/vt_ioctl.c
@@ -672,7 +672,8 @@ int vt_ioctl(struct tty_struct *tty, str
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@xxxxxxxxxxxx */
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
*/
diff -puN include/linux/console_struct.h~vt-refactor-console-sak-processing include/linux/console_struct.h
--- a/include/linux/console_struct.h~vt-refactor-console-sak-processing
+++ a/include/linux/console_struct.h
@@ -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
diff -puN include/linux/tty.h~vt-refactor-console-sak-processing include/linux/tty.h
--- a/include/linux/tty.h~vt-refactor-console-sak-processing
+++ a/include/linux/tty.h
@@ -291,6 +291,7 @@ extern void tty_vhangup(struct tty_struc
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);
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
doc-atomic_add_unless-doesnt-imply-mb-on-failure.patch
vt-refactor-console-sak-processing.patch
pidhash-temporary-debug-checks.patch
-
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