TTY: tty_port questions

Richard Weinberger
2012-03-10T22:26:47Z

[-- Attachment #1: Type: text/plain, Size: 12402 bytes --]

Hi!

While moving UML's console driver to tty_port some strange things happened.
So, I have a few questions. :-)

The original driver did not implement tty_operations->hangup().
If I implement it and call tty_port_hangup(), as Alan suggested,
the login fails on all TTYs except tty0.
It fails because the opened TTY returns EIO upon read()/write() after /bin/login
called vhangup().

The call chain is:
vhangup() -> tty_vhangup_self() -> tty_vhangup() -> __tty_hangup()

Within __tty_hangup() something happens that I don't fully understand:

if (cons_filp) {
if (tty->ops->close)
for (n = 0; n < closecount; n++)
tty->ops->close(tty, cons_filp);
} else if (tty->ops->hangup)
(tty->ops->hangup)(tty);

Login on tty0 works because cons_filp is not NULL and tty->ops->close() is called.
On the other hand login fails on every other TTY because cons_filp remains NULL
and the TTY hangs up.

Is there something missing in my hangup function?

If I omit tty_operations->hangup() and leave it, like the old driver, NULL non-tty0 TTYs cannot
be opened. (getty terminates immediately because it cannot open any TTY.)
open() retuns -EIO because the TTY_CLOSING is set in tty->flags.

How can this be?

Another fun fact is that the above noted problems do not happen on Debian.
Because Debian's /bin/login does not call vhangup().

Thanks,
//richard

--
diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index c1cf220..24de04c 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -19,19 +19,29 @@ static irqreturn_t line_interrupt(int irq, void *data)
{
struct chan *chan = data;
struct line *line = chan->line;
+ struct tty_struct *tty;
+
+ if (line) {
+ tty = tty_port_tty_get(&line->port);
+ chan_interrupt(&line->chan_list, &line->task, tty, irq);
+ tty_kref_put(tty);
+ }

- if (line)
- chan_interrupt(&line->chan_list, &line->task, line->tty, irq);
return IRQ_HANDLED;
}

static void line_timer_cb(struct work_struct *work)
{
struct line *line = container_of(work, struct line, task.work);
+ struct tty_struct *tty;

- if (!line->throttled)
- chan_interrupt(&line->chan_list, &line->task, line->tty,
+ if (!line->throttled) {
+ tty = tty_port_tty_get(&line->port);
+ chan_interrupt(&line->chan_list, &line->task, tty,
line->driver->read_irq);
+
+ tty_kref_put(tty);
+ }
}

/*
@@ -343,7 +353,7 @@ static irqreturn_t line_write_interrupt(int irq, void *data)
{
struct chan *chan = data;
struct line *line = chan->line;
- struct tty_struct *tty = line->tty;
+ struct tty_struct *tty = tty_port_tty_get(&line->port);
int err;

/*
@@ -354,6 +364,7 @@ static irqreturn_t line_write_interrupt(int irq, void *data)
spin_lock(&line->lock);
err = flush_buffer(line);
if (err == 0) {
+ tty_kref_put(tty);
return IRQ_NONE;
} else if (err < 0) {
line->head = line->buffer;
@@ -365,9 +376,36 @@ static irqreturn_t line_write_interrupt(int irq, void *data)
return IRQ_NONE;

tty_wakeup(tty);
+ tty_kref_put(tty);
return IRQ_HANDLED;
}

+static int line_activate(struct tty_port *port, struct tty_struct *tty)
+{
+ int ret;
+ struct line *line = tty->driver_data;
+
+ ret = enable_chan(line);
+ if (ret)
+ return ret;
+
+ INIT_DELAYED_WORK(&line->task, line_timer_cb);
+
+ if (!line->sigio) {
+ chan_enable_winch(&line->chan_list, tty);
+ line->sigio = 1;
+ }
+
+ chan_window_size(&line->chan_list, &tty->winsize.ws_row,
+ &tty->winsize.ws_col);
+
+ return 0;
+}
+
+static const struct tty_port_operations line_port_ops = {
+ .activate = line_activate,
+};
+
int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
{
const struct line_driver *driver = line->driver;
@@ -404,81 +442,49 @@ int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
* first open or last close. Otherwise, open and close just return.
*/

-int line_open(struct line *lines, struct tty_struct *tty)
+int line_open(struct tty_struct *tty, struct file *filp)
{
- struct line *line = &lines[tty->index];
- int err = -ENODEV;
+ struct line *line = tty->driver_data;
+ return tty_port_open(&line->port, tty, filp);
+}

- spin_lock(&line->count_lock);
- if (!line->valid)
- goto out_unlock;
+int line_install(struct tty_driver *driver, struct tty_struct *tty, struct line *line)
+{
+ int ret = tty_init_termios(tty);
+ if (ret)
+ return ret;

- err = 0;
- if (line->count++)
- goto out_unlock;
+ tty_driver_kref_get(driver);
+ tty->count++;
+ driver->ttys[tty->index] = tty;

- BUG_ON(tty->driver_data);
tty->driver_data = line;
- line->tty = tty;
-
- spin_unlock(&line->count_lock);
- err = enable_chan(line);
- if (err) /* line_close() will be called by our caller */
- return err;
-
- INIT_DELAYED_WORK(&line->task, line_timer_cb);
-
- if (!line->sigio) {
- chan_enable_winch(&line->chan_list, tty);
- line->sigio = 1;
- }
-
- chan_window_size(&line->chan_list, &tty->winsize.ws_row,
- &tty->winsize.ws_col);

return 0;
-
-out_unlock:
- spin_unlock(&line->count_lock);
- return err;
}

static void unregister_winch(struct tty_struct *tty);

-void line_close(struct tty_struct *tty, struct file * filp)
+void line_cleanup(struct tty_struct *tty)
{
struct line *line = tty->driver_data;

- /*
- * If line_open fails (and tty->driver_data is never set),
- * tty_open will call line_close. So just return in this case.
- */
- if (line == NULL)
- return;
-
- /* We ignore the error anyway! */
- flush_buffer(line);
-
- spin_lock(&line->count_lock);
- BUG_ON(!line->valid);
-
- if (--line->count)
- goto out_unlock;
-
- line->tty = NULL;
- tty->driver_data = NULL;
-
- spin_unlock(&line->count_lock);
-
if (line->sigio) {
unregister_winch(tty);
line->sigio = 0;
}
+}

- return;
+void line_close(struct tty_struct *tty, struct file * filp)
+{
+ struct line *line = tty->driver_data;
+ tty_port_close(&line->port, tty, filp);
+}

-out_unlock:
- spin_unlock(&line->count_lock);
+void line_hangup(struct tty_struct *tty)
+{
+ struct line *line = tty->driver_data;
+ tty_port_hangup(&line->port);
}

void close_lines(struct line *lines, int nlines)
@@ -495,13 +501,6 @@ static int setup_one_line(struct line *lines, int n, char *init, int init_prio,
struct line *line = &lines[n];
int err = -EINVAL;

- spin_lock(&line->count_lock);
-
- if (line->count) {
- *error_out = "Device is already open";
- goto out;
- }
-
if (line->init_pri <= init_prio) {
line->init_pri = init_prio;
if (!strcmp(init, "none"))
@@ -512,8 +511,7 @@ static int setup_one_line(struct line *lines, int n, char *init, int init_prio,
}
}
err = 0;
-out:
- spin_unlock(&line->count_lock);
+
return err;
}

@@ -598,6 +596,7 @@ int line_get_config(char *name, struct line *lines, unsigned int num, char *str,
struct line *line;
char *end;
int dev, n = 0;
+ struct tty_struct *tty;

dev = simple_strtoul(name, &end, 0);
if ((*end != '\0') || (end == name)) {
@@ -612,13 +611,15 @@ int line_get_config(char *name, struct line *lines, unsigned int num, char *str,

line = &lines[dev];

- spin_lock(&line->count_lock);
+ tty = tty_port_tty_get(&line->port);
+
if (!line->valid)
CONFIG_CHUNK(str, size, n, "none", 1);
- else if (line->tty == NULL)
+ else if (tty == NULL)
CONFIG_CHUNK(str, size, n, line->init_str, 1);
else n = chan_config_string(&line->chan_list, str, size, error_out);
- spin_unlock(&line->count_lock);
+
+ tty_kref_put(tty);

return n;
}
@@ -678,8 +679,8 @@ struct tty_driver *register_lines(struct line_driver *line_driver,
}

for(i = 0; i < nlines; i++) {
- if (!lines[i].valid)
- tty_unregister_device(driver, i);
+ tty_port_init(&lines[i].port);
+ lines[i].port.ops = &line_port_ops;
}

mconsole_register_dev(&line_driver->mc);
@@ -805,7 +806,6 @@ void register_winch_irq(int fd, int tty_fd, int pid, struct tty_struct *tty,
.pid = pid,
.tty = tty,
.stack = stack });
-
if (um_request_irq(WINCH_IRQ, fd, IRQ_READ, winch_interrupt,
IRQF_DISABLED | IRQF_SHARED | IRQF_SAMPLE_RANDOM,
"winch", winch) < 0) {
diff --git a/arch/um/drivers/line.h b/arch/um/drivers/line.h
index 63df3ca..54adfc6 100644
--- a/arch/um/drivers/line.h
+++ b/arch/um/drivers/line.h
@@ -31,9 +31,8 @@ struct line_driver {
};

struct line {
- struct tty_struct *tty;
- spinlock_t count_lock;
- unsigned long count;
+ struct tty_port port;
+
int valid;

char *init_str;
@@ -59,15 +58,17 @@ struct line {
};

#define LINE_INIT(str, d) \
- { .count_lock = __SPIN_LOCK_UNLOCKED((str).count_lock), \
- .init_str = str, \
+ { .init_str = str, \
.init_pri = INIT_STATIC, \
.valid = 1, \
.lock = __SPIN_LOCK_UNLOCKED((str).lock), \
.driver = d }

extern void line_close(struct tty_struct *tty, struct file * filp);
-extern int line_open(struct line *lines, struct tty_struct *tty);
+extern int line_open(struct tty_struct *tty, struct file *filp);
+extern int line_install(struct tty_driver *driver, struct tty_struct *tty, struct line *line);
+extern void line_cleanup(struct tty_struct *tty);
+extern void line_hangup(struct tty_struct *tty);
extern int line_setup(struct line *lines, unsigned int sizeof_lines,
char *init, char **error_out);
extern int line_write(struct tty_struct *tty, const unsigned char *buf,
diff --git a/arch/um/drivers/ssl.c b/arch/um/drivers/ssl.c
index 9d8c20a..89fdecb 100644
--- a/arch/um/drivers/ssl.c
+++ b/arch/um/drivers/ssl.c
@@ -92,17 +92,6 @@ static int ssl_remove(int n, char **error_out)
error_out);
}

-static int ssl_open(struct tty_struct *tty, struct file *filp)
-{
- int err = line_open(serial_lines, tty);
-
- if (err)
- printk(KERN_ERR "Failed to open serial line %d, err = %d\n",
- tty->index, err);
-
- return err;
-}
-
#if 0
static void ssl_flush_buffer(struct tty_struct *tty)
{
@@ -124,8 +113,13 @@ void ssl_hangup(struct tty_struct *tty)
}
#endif

+static int ssl_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+ return line_install(driver, tty, &serial_lines[tty->index]);
+}
+
static const struct tty_operations ssl_ops = {
- .open = ssl_open,
+ .open = line_open,
.close = line_close,
.write = line_write,
.put_char = line_put_char,
@@ -134,9 +128,12 @@ static const struct tty_operations ssl_ops = {
.flush_buffer = line_flush_buffer,
.flush_chars = line_flush_chars,
.set_termios = line_set_termios,
- .ioctl = line_ioctl,
+ .ioctl = line_ioctl,
.throttle = line_throttle,
.unthrottle = line_unthrottle,
+ .install = ssl_install,
+ .cleanup = line_cleanup,
+ .hangup = line_hangup,
#if 0
.stop = ssl_stop,
.start = ssl_start,
diff --git a/arch/um/drivers/stdio_console.c b/arch/um/drivers/stdio_console.c
index 088776f..4c78c78 100644
--- a/arch/um/drivers/stdio_console.c
+++ b/arch/um/drivers/stdio_console.c
@@ -97,7 +97,7 @@ static int con_remove(int n, char **error_out)

static int con_open(struct tty_struct *tty, struct file *filp)
{
- int err = line_open(vts, tty);
+ int err = line_open(tty, filp);
if (err)
printk(KERN_ERR "Failed to open console %d, err = %d\n",
tty->index, err);
@@ -105,11 +105,17 @@ static int con_open(struct tty_struct *tty, struct file *filp)
return err;
}

+static int con_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+ return line_install(driver, tty, &vts[tty->index]);
+}
+
/* Set in an initcall, checked in an exitcall */
static int con_init_done = 0;

static const struct tty_operations console_ops = {
.open = con_open,
+ .install = con_install,
.close = line_close,
.write = line_write,
.put_char = line_put_char,
@@ -121,6 +127,8 @@ static const struct tty_operations console_ops = {
.ioctl = line_ioctl,
.throttle = line_throttle,
.unthrottle = line_unthrottle,
+ .cleanup = line_cleanup,
+ .hangup = line_hangup,
};

static void uml_console_write(struct console *console, const char *string,

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 490 bytes --]