Messages in this thread | | | Date | Mon, 25 Oct 2010 09:51:25 +0200 | From | "Dr. Werner Fink" <> | Subject | Re: [PATCH 28/49] tty: Add a new file /proc/tty/consoles |
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On Sat, Oct 23, 2010 at 01:40:24PM +0200, Jiri Slaby wrote: > On 10/22/2010 08:21 PM, Greg Kroah-Hartman wrote: > > +/* > > + * Used for open /proc/tty/consoles. Before this detect > > + * the device ID of file descriptor 0 of the current > > + * reading task if a character device... > > + */ > > +static int tty_consoles_open(struct inode *inode, struct file *file) > > +{ > > + struct files_struct *curfiles; > > + > > + current_dev = 0; > > + curfiles = get_files_struct(current); > > + if (curfiles) { > > + const struct file *curfp; > > + spin_lock(&curfiles->file_lock); > > + curfp = fcheck_files(curfiles, 0); > > + if (curfp && curfp->private_data) { > > + const struct inode *inode; > > + dget(curfp->f_dentry); > > + inode = curfp->f_dentry->d_inode; > > + if (S_ISCHR(inode->i_mode)) { > > + struct tty_struct *tty; > > + tty = (struct tty_struct *)curfp->private_data; > > + if (tty && tty->magic == TTY_MAGIC) { > > Ah, I've just understood what this code does. It seems, that the 'tty' > at this point may be already freed (e.g. people don't set private_data > to NULL). Please explain in the code why it can't... > > Maybe I wouldn't bother with marking the "current" console by star at > all as it seems not to pay off.
This is the main reason for what I've done this patch: To see on which console line the reading process is located. Please do not skip this part as this is currently the only way to detect the real console below /dev/console ... it could be used in user space: e.g. in plymouth or bootlogd (to deterime the main console) or sulogin (to be able to provide a prompt on all console lines).
> > > + tty = tty_pair_get_tty(tty); > > + current_dev = tty_devnum(tty); > > + } > > + } > > + dput(curfp->f_dentry); > > + } > > + spin_unlock(&curfiles->file_lock); > > + put_files_struct(curfiles); > > + } > > + return seq_open(file, &tty_consoles_op); > > +}
Werner
-- "Having a smoking section in a restaurant is like having a peeing section in a swimming pool." -- Edward Burr
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