[PATCH] tty: update the tty layer to work with struct pid

Of kernel subsystems that work with pids the tty layer is probably the largest
consumer.  But it has the nice virtue that the assiation with a session only
lasts until the session leader exits.  Which means that no reference counting
is required.  So using struct pid winds up being a simple optimization to
avoid hash table lookups.

In the long term the use of pid_nr also ensures that when we have multiple pid
spaces mixed everything will work correctly.
Signed-off-by: Eric W. Biederman <eric@maxwell.lnxi.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/um/drivers/line.c

@@ -774,7 +774,7 @@ static irqreturn_t winch_interrupt(int irq, void *data)
 		line = tty->driver_data;
 		chan_window_size(&line->chan_list, &tty->winsize.ws_row,
 				 &tty->winsize.ws_col);
-		kill_pg(tty->pgrp, SIGWINCH, 1);
+		kill_pgrp(tty->pgrp, SIGWINCH, 1);
 	}
  out:
 	if(winch->fd != -1)

drivers/char/ip2/ip2main.c

@@ -1271,8 +1271,8 @@ static void do_input(struct work_struct *work)
 // code duplicated from n_tty (ldisc)
 static inline void  isig(int sig, struct tty_struct *tty, int flush)
 {
-	if (tty->pgrp > 0)
-		kill_pg(tty->pgrp, sig, 1);
+	if (tty->pgrp)
+		kill_pgrp(tty->pgrp, sig, 1);
 	if (flush || !L_NOFLSH(tty)) {
 		if ( tty->ldisc.flush_buffer )  
 			tty->ldisc.flush_buffer(tty);

drivers/char/n_tty.c

@@ -579,8 +579,8 @@ static void eraser(unsigned char c, struct tty_struct *tty)
  
 static inline void isig(int sig, struct tty_struct *tty, int flush)
 {
-	if (tty->pgrp > 0)
-		kill_pg(tty->pgrp, sig, 1);
+	if (tty->pgrp)
+		kill_pgrp(tty->pgrp, sig, 1);
 	if (flush || !L_NOFLSH(tty)) {
 		n_tty_flush_buffer(tty);
 		if (tty->driver->flush_buffer)
@@ -1184,13 +1184,13 @@ static int job_control(struct tty_struct *tty, struct file *file)
 	/* don't stop on /dev/console */
 	if (file->f_op->write != redirected_tty_write &&
 	    current->signal->tty == tty) {
-		if (tty->pgrp <= 0)
-			printk("read_chan: tty->pgrp <= 0!\n");
-		else if (process_group(current) != tty->pgrp) {
+		if (!tty->pgrp)
+			printk("read_chan: no tty->pgrp!\n");
+		else if (task_pgrp(current) != tty->pgrp) {
 			if (is_ignored(SIGTTIN) ||
 			    is_current_pgrp_orphaned())
 				return -EIO;
-			kill_pg(process_group(current), SIGTTIN, 1);
+			kill_pgrp(task_pgrp(current), SIGTTIN, 1);
 			return -ERESTARTSYS;
 		}
 	}

drivers/char/vt.c

@@ -866,8 +866,8 @@ int vc_resize(struct vc_data *vc, unsigned int cols, unsigned int lines)
 		ws.ws_col = vc->vc_cols;
 		ws.ws_ypixel = vc->vc_scan_lines;
 		if ((ws.ws_row != cws->ws_row || ws.ws_col != cws->ws_col) &&
-		    vc->vc_tty->pgrp > 0)
-			kill_pg(vc->vc_tty->pgrp, SIGWINCH, 1);
+		    vc->vc_tty->pgrp)
+			kill_pgrp(vc->vc_tty->pgrp, SIGWINCH, 1);
 		*cws = ws;
 	}
 

fs/proc/array.c

@@ -351,7 +351,7 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole)
 		struct signal_struct *sig = task->signal;
 
 		if (sig->tty) {
-			tty_pgrp = sig->tty->pgrp;
+			tty_pgrp = pid_nr(sig->tty->pgrp);
 			tty_nr = new_encode_dev(tty_devnum(sig->tty));
 		}
 

include/linux/init_task.h

@@ -66,7 +66,7 @@
 	.cpu_timers	= INIT_CPU_TIMERS(sig.cpu_timers),		\
 	.rlim		= INIT_RLIMITS,					\
 	.pgrp		= 1,						\
-	.tty_old_pgrp   = 0,						\
+	.tty_old_pgrp   = NULL,						\
 	{ .__session      = 1},						\
 }
 

include/linux/sched.h

@@ -436,7 +436,7 @@ struct signal_struct {
 
 	/* job control IDs */
 	pid_t pgrp;
-	pid_t tty_old_pgrp;
+	struct pid *tty_old_pgrp;
 
 	union {
 		pid_t session __deprecated;

include/linux/tty.h

@@ -197,8 +197,8 @@ struct tty_struct {
 	struct mutex termios_mutex;
 	struct ktermios *termios, *termios_locked;
 	char name[64];
-	int pgrp;
-	int session;
+	struct pid *pgrp;
+	struct pid *session;
 	unsigned long flags;
 	int count;
 	struct winsize winsize;

kernel/fork.c

@@ -869,7 +869,7 @@ static inline int copy_signal(unsigned long clone_flags, struct task_struct * ts
 	sig->it_prof_incr = cputime_zero;
 
 	sig->leader = 0;	/* session leadership doesn't inherit */
-	sig->tty_old_pgrp = 0;
+	sig->tty_old_pgrp = NULL;
 
 	sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 	sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;

kernel/sys.c

@@ -1510,7 +1510,6 @@ asmlinkage long sys_setsid(void)
 
 	spin_lock(&group_leader->sighand->siglock);
 	group_leader->signal->tty = NULL;
-	group_leader->signal->tty_old_pgrp = 0;
 	spin_unlock(&group_leader->sighand->siglock);
 
 	err = process_group(group_leader);