pty: show associative slave of ptmx in fdinfo

This patch adds "tty-index" field to /proc/PID/fdinfo/N if N
specifies /dev/ptmx. The field shows the index of associative
slave pts.

Though a minor number is given for each pts instance, ptmx is not.
It means there is no way in user-space to know the association between
file descriptors for pts/n and ptmx. (n = 0, 1, ...)

This is different from pipe. About pipe such association can be solved
by inode of pipefs.

Providing the way to know the association between pts/n and ptmx helps
users understand the status of running system. lsof can utilize this field.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Masatake YAMATO 2017-07-18 06:27:59 +09:00 committed by Greg Kroah-Hartman
parent 199e717f25
commit d01c3289e7
3 changed files with 18 additions and 1 deletions

View file

@ -243,6 +243,7 @@
#include <linux/list.h>
#include <linux/cdev.h>
#include <linux/termios.h>
#include <linux/seq_file.h>
struct tty_struct;
struct tty_driver;
@ -285,6 +286,7 @@ struct tty_operations {
int (*set_termiox)(struct tty_struct *tty, struct termiox *tnew);
int (*get_icount)(struct tty_struct *tty,
struct serial_icounter_struct *icount);
void (*show_fdinfo)(struct tty_struct *tty, struct seq_file *m);
#ifdef CONFIG_CONSOLE_POLL
int (*poll_init)(struct tty_driver *driver, int line, char *options);
int (*poll_get_char)(struct tty_driver *driver, int line);