lkml.org 
[lkml]   [2011]   [Feb]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 09/10] n_tracerouter ldisc driver.
On Thu, 24 Feb 2011, james_p_freyensee@linux.intel.com wrote:
> +
> +/**
> + * tracerouter_alloc
> + *
> + * Allocates the structure needed for this ldisc.
> + */
> +static struct tracerouter_data *tracerouter_alloc(void)
> +{
> + struct tracerouter_data *tptr = kzalloc(
> + sizeof(struct tracerouter_data),
> + GFP_KERNEL);
> + if (tptr == NULL)
> + return NULL;
> + tptr->opencalled = 0;

Wheeee!

You first alloc it with kzalloc and then clear the already zero member
again ?

That whole crap condenses down to:

return kzalloc(sizeof(*tptr), GFP_KERNEL);

Which hardly justfies a separate function

> + return tptr;
> +}
> +
> +/**
> + * n_tracerouter_open() - Called when a tty is opened by a SW entity.
> + * @tty: terminal device to the ldisc.
> + *
> + * Return:
> + * 0 for success.
> + *
> + * Caveats: This should only be opened one time per SW entity.
> + */
> +static int n_tracerouter_open(struct tty_struct *tty)
> +{
> + int retval = -EEXIST;
> +
> + mutex_lock(&routelock);
> + if (tr_data->opencalled == 0) {
> +
> + tr_data->kref_tty = tty_kref_get(tty);
> + if (tr_data->kref_tty == NULL)
> + retval = -EFAULT;
> + else {

Please use braces for the if as well. It's just irritating not to have
them before the else.

> + tr_data->opencalled = 1;
> + tty->disc_data = tr_data;
> + tty->receive_room = RECEIVE_ROOM;
> + tty_driver_flush_buffer(tty);
> + retval = 0;
> + }
> + }
> + mutex_unlock(&routelock);
> + return retval;
> +}
> +
> +/**
> + * n_tracerouter_close() - close connection
> + * @tty: terminal device to the ldisc.
> + *
> + * Called when a software entity wants to close a connection.
> + */
> +static void n_tracerouter_close(struct tty_struct *tty)
> +{
> + struct tracerouter_data *tptr = tty->disc_data;
> +
> + WARN_ON(tptr->kref_tty != tr_data->kref_tty);
> + tty_driver_flush_buffer(tty);

That code probably never run with lockdep as you would get a potential
deadlock warning. See n_tracerouter_open().

Though the deadlock cannot happen as you are protected by
tr_data->opencalled it does not make it more correct.

> + mutex_lock(&routelock);
> + tty_kref_put(tr_data->kref_tty);
> + tr_data->kref_tty = NULL;
> + tr_data->opencalled = 0;
> + tty->disc_data = NULL;
> + mutex_unlock(&routelock);
> +}
> +

Thanks,

tglx


\
 
 \ /
  Last update: 2011-02-24 20:23    [W:0.065 / U:0.192 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site