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[S390] 3270: lock dependency fixes
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Lockdep found a problem with the lock order of the view lock and the
ccw device lock. raw3270_activate_view/raw3270_deactivate_view first
take the ccw device lock then call the activate/deactivate functions
of the view which take view lock. The update functions of the
con3270/tty3270 view will first take the view lock, then take the
ccw device lock. To fix this the activate/deactivate functions are
changed to avoid taking the view lock by moving the functions calls
that modify the 3270 output buffer to the update function which is
called by a timer.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Martin Schwidefsky committed Jun 12, 2009
1 parent fcf7581 commit 205d7ab
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Showing 2 changed files with 32 additions and 48 deletions.
38 changes: 14 additions & 24 deletions drivers/s390/char/con3270.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,7 @@ static struct con3270 *condev;
#define CON_UPDATE_ERASE 1 /* Use EWRITEA instead of WRITE. */
#define CON_UPDATE_LIST 2 /* Update lines in tty3270->update. */
#define CON_UPDATE_STATUS 4 /* Update status line. */
#define CON_UPDATE_ALL 7
#define CON_UPDATE_ALL 8 /* Recreate screen. */

static void con3270_update(struct con3270 *);

Expand All @@ -73,18 +73,10 @@ static void con3270_update(struct con3270 *);
*/
static void con3270_set_timer(struct con3270 *cp, int expires)
{
if (expires == 0) {
if (timer_pending(&cp->timer))
del_timer(&cp->timer);
return;
}
if (timer_pending(&cp->timer) &&
mod_timer(&cp->timer, jiffies + expires))
return;
cp->timer.function = (void (*)(unsigned long)) con3270_update;
cp->timer.data = (unsigned long) cp;
cp->timer.expires = jiffies + expires;
add_timer(&cp->timer);
if (expires == 0)
del_timer(&cp->timer);
else
mod_timer(&cp->timer, jiffies + expires);
}

/*
Expand Down Expand Up @@ -225,6 +217,12 @@ con3270_update(struct con3270 *cp)

spin_lock_irqsave(&cp->view.lock, flags);
updated = 0;
if (cp->update_flags & CON_UPDATE_ALL) {
con3270_rebuild_update(cp);
con3270_update_status(cp);
cp->update_flags = CON_UPDATE_ERASE | CON_UPDATE_LIST |
CON_UPDATE_STATUS;
}
if (cp->update_flags & CON_UPDATE_ERASE) {
/* Use erase write alternate to initialize display. */
raw3270_request_set_cmd(wrq, TC_EWRITEA);
Expand Down Expand Up @@ -302,7 +300,6 @@ con3270_read_tasklet(struct raw3270_request *rrq)
deactivate = 1;
break;
case 0x6d: /* clear: start from scratch. */
con3270_rebuild_update(cp);
cp->update_flags = CON_UPDATE_ALL;
con3270_set_timer(cp, 1);
break;
Expand Down Expand Up @@ -382,30 +379,21 @@ con3270_issue_read(struct con3270 *cp)
static int
con3270_activate(struct raw3270_view *view)
{
unsigned long flags;
struct con3270 *cp;

cp = (struct con3270 *) view;
spin_lock_irqsave(&cp->view.lock, flags);
cp->nr_up = 0;
con3270_rebuild_update(cp);
con3270_update_status(cp);
cp->update_flags = CON_UPDATE_ALL;
con3270_set_timer(cp, 1);
spin_unlock_irqrestore(&cp->view.lock, flags);
return 0;
}

static void
con3270_deactivate(struct raw3270_view *view)
{
unsigned long flags;
struct con3270 *cp;

cp = (struct con3270 *) view;
spin_lock_irqsave(&cp->view.lock, flags);
del_timer(&cp->timer);
spin_unlock_irqrestore(&cp->view.lock, flags);
}

static int
Expand Down Expand Up @@ -504,6 +492,7 @@ con3270_write(struct console *co, const char *str, unsigned int count)
con3270_cline_end(cp);
}
/* Setup timer to output current console buffer after 1/10 second */
cp->nr_up = 0;
if (cp->view.dev && !timer_pending(&cp->timer))
con3270_set_timer(cp, HZ/10);
spin_unlock_irqrestore(&cp->view.lock,flags);
Expand Down Expand Up @@ -624,7 +613,8 @@ con3270_init(void)

INIT_LIST_HEAD(&condev->lines);
INIT_LIST_HEAD(&condev->update);
init_timer(&condev->timer);
setup_timer(&condev->timer, (void (*)(unsigned long)) con3270_update,
(unsigned long) condev);
tasklet_init(&condev->readlet,
(void (*)(unsigned long)) con3270_read_tasklet,
(unsigned long) condev->read);
Expand Down
42 changes: 18 additions & 24 deletions drivers/s390/char/tty3270.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -112,7 +112,7 @@ struct tty3270 {
#define TTY_UPDATE_LIST 2 /* Update lines in tty3270->update. */
#define TTY_UPDATE_INPUT 4 /* Update input line. */
#define TTY_UPDATE_STATUS 8 /* Update status line. */
#define TTY_UPDATE_ALL 15
#define TTY_UPDATE_ALL 16 /* Recreate screen. */

static void tty3270_update(struct tty3270 *);

Expand All @@ -121,19 +121,10 @@ static void tty3270_update(struct tty3270 *);
*/
static void tty3270_set_timer(struct tty3270 *tp, int expires)
{
if (expires == 0) {
if (timer_pending(&tp->timer) && del_timer(&tp->timer))
raw3270_put_view(&tp->view);
return;
}
if (timer_pending(&tp->timer) &&
mod_timer(&tp->timer, jiffies + expires))
return;
raw3270_get_view(&tp->view);
tp->timer.function = (void (*)(unsigned long)) tty3270_update;
tp->timer.data = (unsigned long) tp;
tp->timer.expires = jiffies + expires;
add_timer(&tp->timer);
if (expires == 0)
del_timer(&tp->timer);
else
mod_timer(&tp->timer, jiffies + expires);
}

/*
Expand Down Expand Up @@ -337,7 +328,6 @@ tty3270_write_callback(struct raw3270_request *rq, void *data)
tp = (struct tty3270 *) rq->view;
if (rq->rc != 0) {
/* Write wasn't successfull. Refresh all. */
tty3270_rebuild_update(tp);
tp->update_flags = TTY_UPDATE_ALL;
tty3270_set_timer(tp, 1);
}
Expand Down Expand Up @@ -366,6 +356,12 @@ tty3270_update(struct tty3270 *tp)

spin_lock(&tp->view.lock);
updated = 0;
if (tp->update_flags & TTY_UPDATE_ALL) {
tty3270_rebuild_update(tp);
tty3270_update_status(tp);
tp->update_flags = TTY_UPDATE_ERASE | TTY_UPDATE_LIST |
TTY_UPDATE_INPUT | TTY_UPDATE_STATUS;
}
if (tp->update_flags & TTY_UPDATE_ERASE) {
/* Use erase write alternate to erase display. */
raw3270_request_set_cmd(wrq, TC_EWRITEA);
Expand Down Expand Up @@ -425,7 +421,6 @@ tty3270_update(struct tty3270 *tp)
xchg(&tp->write, wrq);
}
spin_unlock(&tp->view.lock);
raw3270_put_view(&tp->view);
}

/*
Expand Down Expand Up @@ -570,7 +565,6 @@ tty3270_read_tasklet(struct raw3270_request *rrq)
tty3270_set_timer(tp, 1);
} else if (tp->input->string[0] == 0x6d) {
/* Display has been cleared. Redraw. */
tty3270_rebuild_update(tp);
tp->update_flags = TTY_UPDATE_ALL;
tty3270_set_timer(tp, 1);
}
Expand Down Expand Up @@ -641,22 +635,20 @@ static int
tty3270_activate(struct raw3270_view *view)
{
struct tty3270 *tp;
unsigned long flags;

tp = (struct tty3270 *) view;
spin_lock_irqsave(&tp->view.lock, flags);
tp->nr_up = 0;
tty3270_rebuild_update(tp);
tty3270_update_status(tp);
tp->update_flags = TTY_UPDATE_ALL;
tty3270_set_timer(tp, 1);
spin_unlock_irqrestore(&tp->view.lock, flags);
return 0;
}

static void
tty3270_deactivate(struct raw3270_view *view)
{
struct tty3270 *tp;

tp = (struct tty3270 *) view;
del_timer(&tp->timer);
}

static int
Expand Down Expand Up @@ -743,6 +735,7 @@ tty3270_free_view(struct tty3270 *tp)
{
int pages;

del_timer_sync(&tp->timer);
kbd_free(tp->kbd);
raw3270_request_free(tp->kreset);
raw3270_request_free(tp->read);
Expand Down Expand Up @@ -889,7 +882,8 @@ tty3270_open(struct tty_struct *tty, struct file * filp)
INIT_LIST_HEAD(&tp->update);
INIT_LIST_HEAD(&tp->rcl_lines);
tp->rcl_max = 20;
init_timer(&tp->timer);
setup_timer(&tp->timer, (void (*)(unsigned long)) tty3270_update,
(unsigned long) tp);
tasklet_init(&tp->readlet,
(void (*)(unsigned long)) tty3270_read_tasklet,
(unsigned long) tp->read);
Expand Down

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