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Subject[RFC] add module reference to struct tty_driver
In digging into the tty layer locking, I noticed that the tty layer
doesn't handle module reference counting for any tty drivers. Well, I've
known this for a long time, just finally got around to fixing it :)
Here's a patch against 2.5.56 that should fix this issue (works for
me...)

Comments? If no one objects, I'll send it on to Linus, and add support
for this to a number of tty drivers that commonly get built as modules.

thanks,

greg k-h


# TTY: add module reference counting for tty drivers.

diff -Nru a/drivers/char/tty_io.c b/drivers/char/tty_io.c
--- a/drivers/char/tty_io.c Sun Jan 12 21:46:53 2003
+++ b/drivers/char/tty_io.c Sun Jan 12 21:46:53 2003
@@ -833,6 +833,11 @@
* and locked termios may be retained.)
*/

+ if (!try_module_get(driver->owner)) {
+ retval = -ENODEV;
+ goto end_init;
+ }
+
o_tty = NULL;
tp = o_tp = NULL;
ltp = o_ltp = NULL;
@@ -991,6 +996,7 @@
free_tty_struct(tty);

fail_no_mem:
+ module_put(driver->owner);
retval = -ENOMEM;
goto end_init;

@@ -1033,6 +1039,7 @@
tty->magic = 0;
(*tty->driver.refcount)--;
list_del(&tty->tty_files);
+ module_put(tty->driver.owner);
free_tty_struct(tty);
}

diff -Nru a/include/linux/tty_driver.h b/include/linux/tty_driver.h
--- a/include/linux/tty_driver.h Sun Jan 12 21:46:53 2003
+++ b/include/linux/tty_driver.h Sun Jan 12 21:46:53 2003
@@ -120,6 +120,7 @@

struct tty_driver {
int magic; /* magic number for this structure */
+ struct module *owner;
const char *driver_name;
const char *name;
int name_base; /* offset of printed name */
-
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