Revert the process group accessor functions. They are buggy, and

cause NULL pointer references in /proc.

Moreover, it's questionable whether the whole thing makes sense at all. 
Per-thread state is good.

Cset exclude: davem@nuts.ninka.net|ChangeSet|20031005193942|01097
Cset exclude: akpm@osdl.org[torvalds]|ChangeSet|20031005180420|42200
Cset exclude: akpm@osdl.org[torvalds]|ChangeSet|20031005180411|42211

arch/ia64/kernel/unaligned.c

@@ -1347,7 +1347,7 @@ ia64_handle_unaligned (unsigned long ifa, struct pt_regs *regs)
 			 * be holding locks...
 			 */
 			if (user_mode(regs))
-				tty_write_message(process_tty(current), buf);
+				tty_write_message(current->tty, buf);
 			buf[len-1] = '\0';	/* drop '\r' */
 			printk(KERN_WARNING "%s", buf);	/* watch for command names containing %s */
 		}

arch/sparc64/solaris/misc.c

@@ -402,7 +402,7 @@ asmlinkage int solaris_procids(int cmd, s32 pid, s32 pgid)
 			   Solaris setpgrp and setsid? */
 			ret = sys_setpgid(0, 0);
 			if (ret) return ret;
-			current->signal->tty = NULL;
+			current->tty = NULL;
 			return process_group(current);
 		}
 	case 2: /* getsid */

drivers/char/n_tty.c

@@ -974,8 +974,7 @@ static ssize_t read_chan(struct tty_struct *tty, struct file *file,
 	/* NOTE: not yet done after every sleep pending a thorough
 	   check of the logic of this change. -- jlc */
 	/* don't stop on /dev/console */
-	if (file->f_op->write != redirected_tty_write &&
-			process_tty(current) == tty) {
+	if (file->f_op->write != redirected_tty_write && current->tty == tty) {
 		if (tty->pgrp <= 0)
 			printk("read_chan: tty->pgrp <= 0!\n");
 		else if (process_group(current) != tty->pgrp) {

drivers/char/rocket.c

@@ -953,7 +953,7 @@ static int rp_open(struct tty_struct *tty, struct file *filp)
 	/*
 	 * Info->count is now 1; so it's safe to sleep now.
 	 */
-	info->session = process_session(current);
+	info->session = current->session;
 	info->pgrp = process_group(current);
 
 	if ((info->flags & ROCKET_INITIALIZED) == 0) {

drivers/char/tty_io.c

@@ -316,7 +316,7 @@ struct tty_driver *get_tty_driver(dev_t device, int *index)
  */
 int tty_check_change(struct tty_struct * tty)
 {
-	if (process_tty(current) != tty)
+	if (current->tty != tty)
 		return 0;
 	if (tty->pgrp <= 0) {
 		printk(KERN_WARNING "tty_check_change: tty->pgrp <= 0!\n");
@@ -483,14 +483,14 @@ void do_tty_hangup(void *data)
 	if (tty->session > 0) {
 		struct list_head *l;
 		for_each_task_pid(tty->session, PIDTYPE_SID, p, l, pid) {
-			if (process_tty(p) == tty)
-				p->signal->tty = NULL;
-			if (!process_session_leader(p))
+			if (p->tty == tty)
+				p->tty = NULL;
+			if (!p->leader)
 				continue;
 			send_group_sig_info(SIGHUP, SEND_SIG_PRIV, p);
 			send_group_sig_info(SIGCONT, SEND_SIG_PRIV, p);
 			if (tty->pgrp > 0)
-				p->signal->tty_old_pgrp = tty->pgrp;
+				p->tty_old_pgrp = tty->pgrp;
 		}
 	}
 	read_unlock(&tasklist_lock);
@@ -567,15 +567,15 @@ void disassociate_ctty(int on_exit)
 
 	lock_kernel();
 
-	tty = process_tty(current);
+	tty = current->tty;
 	if (tty) {
 		tty_pgrp = tty->pgrp;
 		if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)
 			tty_vhangup(tty);
 	} else {
-		if (current->signal->tty_old_pgrp) {
-			kill_pg(current->signal->tty_old_pgrp, SIGHUP, on_exit);
-			kill_pg(current->signal->tty_old_pgrp, SIGCONT, on_exit);
+		if (current->tty_old_pgrp) {
+			kill_pg(current->tty_old_pgrp, SIGHUP, on_exit);
+			kill_pg(current->tty_old_pgrp, SIGCONT, on_exit);
 		}
 		unlock_kernel();	
 		return;
@@ -586,13 +586,13 @@ void disassociate_ctty(int on_exit)
 			kill_pg(tty_pgrp, SIGCONT, on_exit);
 	}
 
-	current->signal->tty_old_pgrp = 0;
+	current->tty_old_pgrp = 0;
 	tty->session = 0;
 	tty->pgrp = -1;
 
 	read_lock(&tasklist_lock);
-	for_each_task_pid(process_session(current), PIDTYPE_SID, p, l, pid)
-		p->signal->tty = NULL;
+	for_each_task_pid(current->session, PIDTYPE_SID, p, l, pid)
+		p->tty = NULL;
 	read_unlock(&tasklist_lock);
 	unlock_kernel();
 }
@@ -1220,10 +1220,10 @@ static void release_dev(struct file * filp)
 
 		read_lock(&tasklist_lock);
 		for_each_task_pid(tty->session, PIDTYPE_SID, p, l, pid)
-			p->signal->tty = NULL;
+			p->tty = NULL;
 		if (o_tty)
 			for_each_task_pid(o_tty->session, PIDTYPE_SID, p,l, pid)
-				p->signal->tty = NULL;
+				p->tty = NULL;
 		read_unlock(&tasklist_lock);
 	}
 
@@ -1294,10 +1294,10 @@ static int tty_open(struct inode * inode, struct file * filp)
 retry_open:
 	noctty = filp->f_flags & O_NOCTTY;
 	if (device == MKDEV(TTYAUX_MAJOR,0)) {
-		if (!process_tty(current))
+		if (!current->tty)
 			return -ENXIO;
-		driver = process_tty(current)->driver;
-		index = process_tty(current)->index;
+		driver = current->tty->driver;
+		index = current->tty->index;
 		filp->f_flags |= O_NONBLOCK; /* Don't let /dev/tty block */
 		/* noctty = 1; */
 		goto got_driver;
@@ -1391,13 +1391,15 @@ static int tty_open(struct inode * inode, struct file * filp)
 			filp->f_op = &tty_fops;
 		goto retry_open;
 	}
-	if (!noctty && process_session_leader(current) &&
-			!process_tty(current) && tty->session == 0) {
+	if (!noctty &&
+	    current->leader &&
+	    !current->tty &&
+	    tty->session == 0) {
 	    	task_lock(current);
-		current->signal->tty = tty;
+		current->tty = tty;
 		task_unlock(current);
-		current->signal->tty_old_pgrp = 0;
-		tty->session = process_session(current);
+		current->tty_old_pgrp = 0;
+		tty->session = current->session;
 		tty->pgrp = process_group(current);
 	}
 	return 0;
@@ -1455,7 +1457,7 @@ static int tiocsti(struct tty_struct *tty, char * arg)
 {
 	char ch, mbz = 0;
 
-	if ((process_tty(current) != tty) && !capable(CAP_SYS_ADMIN))
+	if ((current->tty != tty) && !capable(CAP_SYS_ADMIN))
 		return -EPERM;
 	if (get_user(ch, arg))
 		return -EFAULT;
@@ -1541,14 +1543,14 @@ static int tiocsctty(struct tty_struct *tty, int arg)
 	struct pid *pid;
 	task_t *p;
 
-	if (process_session_leader(current) &&
-			(process_session(current) == tty->session))
+	if (current->leader &&
+	    (current->session == tty->session))
 		return 0;
 	/*
 	 * The process must be a session leader and
 	 * not have a controlling tty already.
 	 */
-	if (!process_session_leader(current) || process_tty(current))
+	if (!current->leader || current->tty)
 		return -EPERM;
 	if (tty->session > 0) {
 		/*
@@ -1562,16 +1564,16 @@ static int tiocsctty(struct tty_struct *tty, int arg)
 
 			read_lock(&tasklist_lock);
 			for_each_task_pid(tty->session, PIDTYPE_SID, p, l, pid)
-				p->signal->tty = NULL;
+				p->tty = NULL;
 			read_unlock(&tasklist_lock);
 		} else
 			return -EPERM;
 	}
 	task_lock(current);
-	current->signal->tty = tty;
+	current->tty = tty;
 	task_unlock(current);
-	current->signal->tty_old_pgrp = 0;
-	tty->session = process_session(current);
+	current->tty_old_pgrp = 0;
+	tty->session = current->session;
 	tty->pgrp = process_group(current);
 	return 0;
 }
@@ -1582,13 +1584,12 @@ static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
 	 * (tty == real_tty) is a cheap way of
 	 * testing if the tty is NOT a master pty.
 	 */
-	if (tty == real_tty && process_tty(current) != real_tty)
+	if (tty == real_tty && current->tty != real_tty)
 		return -ENOTTY;
 	return put_user(real_tty->pgrp, arg);
 }
 
-static int tiocspgrp(struct tty_struct *tty,
-			struct tty_struct *real_tty, pid_t *arg)
+static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t *arg)
 {
 	pid_t pgrp;
 	int retval = tty_check_change(real_tty);
@@ -1597,14 +1598,15 @@ static int tiocspgrp(struct tty_struct *tty,
 		return -ENOTTY;
 	if (retval)
 		return retval;
-	if (!process_tty(current) || (process_tty(current) != real_tty) ||
-			(real_tty->session != process_session(current)))
+	if (!current->tty ||
+	    (current->tty != real_tty) ||
+	    (real_tty->session != current->session))
 		return -ENOTTY;
 	if (get_user(pgrp, (pid_t *) arg))
 		return -EFAULT;
 	if (pgrp < 0)
 		return -EINVAL;
-	if (session_of_pgrp(pgrp) != process_session(current))
+	if (session_of_pgrp(pgrp) != current->session)
 		return -EPERM;
 	real_tty->pgrp = pgrp;
 	return 0;
@@ -1616,7 +1618,7 @@ static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t *
 	 * (tty == real_tty) is a cheap way of
 	 * testing if the tty is NOT a master pty.
 	*/
-	if (tty == real_tty && process_tty(current) != real_tty)
+	if (tty == real_tty && current->tty != real_tty)
 		return -ENOTTY;
 	if (real_tty->session <= 0)
 		return -ENOTTY;
@@ -1774,12 +1776,12 @@ int tty_ioctl(struct inode * inode, struct file * file,
 			clear_bit(TTY_EXCLUSIVE, &tty->flags);
 			return 0;
 		case TIOCNOTTY:
-			if (process_tty(current) != tty)
+			if (current->tty != tty)
 				return -ENOTTY;
-			if (process_session_leader(current))
+			if (current->leader)
 				disassociate_ctty(0);
 			task_lock(current);
-			current->signal->tty = NULL;
+			current->tty = NULL;
 			task_unlock(current);
 			return 0;
 		case TIOCSCTTY:
@@ -1883,10 +1885,10 @@ static void __do_SAK(void *arg)
 		tty->driver->flush_buffer(tty);
 	read_lock(&tasklist_lock);
 	for_each_task_pid(session, PIDTYPE_SID, p, l, pid) {
-		if (process_tty(p) == tty || session > 0) {
+		if (p->tty == tty || session > 0) {
 			printk(KERN_NOTICE "SAK: killed process %d"
-				" (%s): process_session(p)==tty->session\n",
-				p->pid, p->comm);
+			    " (%s): p->session==tty->session\n",
+			    p->pid, p->comm);
 			send_sig(SIGKILL, p, 1);
 			continue;
 		}

drivers/char/vt.c

@@ -2226,7 +2226,7 @@ int tioclinux(struct tty_struct *tty, unsigned long arg)
 
 	if (tty->driver->type != TTY_DRIVER_TYPE_CONSOLE)
 		return -EINVAL;
-	if (process_tty(current) != tty && !capable(CAP_SYS_ADMIN))
+	if (current->tty != tty && !capable(CAP_SYS_ADMIN))
 		return -EPERM;
 	if (get_user(type, (char *)arg))
 		return -EFAULT;

drivers/char/vt_ioctl.c

@@ -380,7 +380,7 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
 	 * to be the owner of the tty, or have CAP_SYS_TTY_CONFIG.
 	 */
 	perm = 0;
-	if (process_tty(current) == tty || capable(CAP_SYS_TTY_CONFIG))
+	if (current->tty == tty || capable(CAP_SYS_TTY_CONFIG))
 		perm = 1;
  
 	kbd = kbd_table + console;
@@ -1188,3 +1188,4 @@ void change_console(unsigned int new_console)
 
 	complete_change_console(new_console);
 }
+

drivers/net/slip.c

@@ -1307,7 +1307,7 @@ static int sl_ioctl(struct net_device *dev,struct ifreq *rq,int cmd)
 		/* Resolve race condition, when ioctl'ing hanged up 
 		   and opened by another process device.
 		 */
-		if (sl->tty != process_tty(current) && sl->pid != current->pid) {
+		if (sl->tty != current->tty && sl->pid != current->pid) {
 			spin_unlock_bh(&sl->lock);
 			return -EPERM;
 		}

fs/binfmt_elf.c

@@ -1084,7 +1084,7 @@ static void fill_prstatus(struct elf_prstatus *prstatus,
 	prstatus->pr_pid = p->pid;
 	prstatus->pr_ppid = p->parent->pid;
 	prstatus->pr_pgrp = process_group(p);
-	prstatus->pr_sid = process_session(p);
+	prstatus->pr_sid = p->session;
 	jiffies_to_timeval(p->utime, &prstatus->pr_utime);
 	jiffies_to_timeval(p->stime, &prstatus->pr_stime);
 	jiffies_to_timeval(p->cutime, &prstatus->pr_cutime);
@@ -1112,7 +1112,7 @@ static void fill_psinfo(struct elf_prpsinfo *psinfo, struct task_struct *p,
 	psinfo->pr_pid = p->pid;
 	psinfo->pr_ppid = p->parent->pid;
 	psinfo->pr_pgrp = process_group(p);
-	psinfo->pr_sid = process_session(p);
+	psinfo->pr_sid = p->session;
 
 	i = p->state ? ffz(~p->state) + 1 : 0;
 	psinfo->pr_state = i;

fs/compat_ioctl.c

@@ -1574,7 +1574,7 @@ static int vt_check(struct file *file)
 	 * To have permissions to do most of the vt ioctls, we either have
 	 * to be the owner of the tty, or super-user.
 	 */
-	if (process_tty(current) == tty || capable(CAP_SYS_ADMIN))
+	if (current->tty == tty || capable(CAP_SYS_ADMIN))
 		return 1;
 	return 0;                                                    
 }

fs/dquot.c

@@ -668,12 +668,12 @@ static void print_warning(struct dquot *dquot, const char warntype)
 
 	if (!need_print_warning(dquot) || (flag && test_and_set_bit(flag, &dquot->dq_flags)))
 		return;
-	tty_write_message(process_tty(current), dquot->dq_sb->s_id);
+	tty_write_message(current->tty, dquot->dq_sb->s_id);
 	if (warntype == ISOFTWARN || warntype == BSOFTWARN)
-		tty_write_message(process_tty(current), ": warning, ");
+		tty_write_message(current->tty, ": warning, ");
 	else
-		tty_write_message(process_tty(current), ": write failed, ");
-	tty_write_message(process_tty(current), quotatypes[dquot->dq_type]);
+		tty_write_message(current->tty, ": write failed, ");
+	tty_write_message(current->tty, quotatypes[dquot->dq_type]);
 	switch (warntype) {
 		case IHARDWARN:
 			msg = " file limit reached.\n";
@@ -694,7 +694,7 @@ static void print_warning(struct dquot *dquot, const char warntype)
 			msg = " block quota exceeded.\n";
 			break;
 	}
-	tty_write_message(process_tty(current), msg);
+	tty_write_message(current->tty, msg);
 }
 
 static inline void flush_warnings(struct dquot **dquots, char *warntype)

fs/exec.c

@@ -596,11 +596,6 @@ static inline int de_thread(struct task_struct *tsk)
 		newsig->group_stop_count = 0;
 		newsig->curr_target = NULL;
 		init_sigpending(&newsig->shared_pending);
-
-		newsig->pgrp = oldsig->pgrp;
-		newsig->session = oldsig->session;
-		newsig->leader = oldsig->leader;
-		newsig->tty_old_pgrp = oldsig->tty_old_pgrp;
 	}
 
 	if (thread_group_empty(current))

fs/open.c

@@ -1035,7 +1035,7 @@ EXPORT_SYMBOL(sys_close);
 asmlinkage long sys_vhangup(void)
 {
 	if (capable(CAP_SYS_TTY_CONFIG)) {
-		tty_vhangup(process_tty(current));
+		tty_vhangup(current->tty);
 		return 0;
 	}
 	return -EPERM;

fs/proc/array.c

@@ -304,9 +304,9 @@ int proc_pid_stat(struct task_struct *task, char * buffer)
 	mm = task->mm;
 	if(mm)
 		mm = mmgrab(mm);
-	if (process_tty(task)) {
-		tty_pgrp = process_tty(task)->pgrp;
-		tty_nr = new_encode_dev(tty_devnum(process_tty(task)));
+	if (task->tty) {
+		tty_pgrp = task->tty->pgrp;
+		tty_nr = new_encode_dev(tty_devnum(task->tty));
 	}
 	task_unlock(task);
 	if (mm) {
@@ -345,7 +345,7 @@ int proc_pid_stat(struct task_struct *task, char * buffer)
 		state,
 		ppid,
 		process_group(task),
-		process_session(task),
+		task->session,
 		tty_nr,
 		tty_pgrp,
 		task->flags,

include/linux/sched.h

@@ -264,15 +264,6 @@ struct signal_struct {
 
 	/* thread group stop support, overloads group_exit_code too */
 	int			group_stop_count;
-
-	/* job control IDs */
-	pid_t pgrp;
-	pid_t tty_old_pgrp;
-	pid_t session;
-	/* boolean value for session group leader */
-	int leader;
-
-	struct tty_struct *tty; /* NULL if no tty */
 };
 
 /*
@@ -375,7 +366,12 @@ struct task_struct {
 	unsigned long personality;
 	int did_exec:1;
 	pid_t pid;
+	pid_t __pgrp;		/* Accessed via process_group() */
+	pid_t tty_old_pgrp;
+	pid_t session;
 	pid_t tgid;
+	/* boolean value for session group leader */
+	int leader;
 	/* 
 	 * pointers to (original) parent process, youngest child, younger sibling,
 	 * older sibling, respectively.  (p->father can be replaced with 
@@ -419,6 +415,7 @@ struct task_struct {
 	char comm[16];
 /* file system info */
 	int link_count, total_link_count;
+	struct tty_struct *tty; /* NULL if no tty */
 /* ipc stuff */
 	struct sysv_sem sysvsem;
 /* CPU-specific state of this task */
@@ -471,22 +468,7 @@ struct task_struct {
 
 static inline pid_t process_group(struct task_struct *tsk)
 {
-	return tsk->signal->pgrp;
-}
-
-static inline pid_t process_session(struct task_struct *tsk)
-{
-	return tsk->signal->session;
-}
-
-static inline int process_session_leader(struct task_struct *tsk)
-{
-	return tsk->signal->leader;
-}
-
-static inline struct tty_struct *process_tty(struct task_struct *tsk)
-{
-	return tsk->signal->tty;
+	return tsk->group_leader->__pgrp;
 }
 
 extern void __put_task_struct(struct task_struct *tsk);

kernel/acct.c

@@ -343,7 +343,7 @@ static void do_acct_process(long exitcode, struct file *file)
 	/* we really need to bite the bullet and change layout */
 	ac.ac_uid = current->uid;
 	ac.ac_gid = current->gid;
-	ac.ac_tty = process_tty(current) ? old_encode_dev(tty_devnum(process_tty(current))) : 0;
+	ac.ac_tty = current->tty ? old_encode_dev(tty_devnum(current->tty)) : 0;
 
 	ac.ac_flag = 0;
 	if (current->flags & PF_FORKNOEXEC)

kernel/exit.c

@@ -119,13 +119,13 @@ int session_of_pgrp(int pgrp)
 
 	read_lock(&tasklist_lock);
 	for_each_task_pid(pgrp, PIDTYPE_PGID, p, l, pid)
-		if (process_session(p) > 0) {
-			sid = process_session(p);
+		if (p->session > 0) {
+			sid = p->session;
 			goto out;
 		}
 	p = find_task_by_pid(pgrp);
 	if (p)
-		sid = process_session(p);
+		sid = p->session;
 out:
 	read_unlock(&tasklist_lock);
 	
@@ -153,7 +153,7 @@ static int will_become_orphaned_pgrp(int pgrp, task_t *ignored_task)
 				|| p->real_parent->pid == 1)
 			continue;
 		if (process_group(p->real_parent) != pgrp
-			    && process_session(p->real_parent) == process_session(p)) {
+			    && p->real_parent->session == p->session) {
 			ret = 0;
 			break;
 		}
@@ -242,14 +242,14 @@ void __set_special_pids(pid_t session, pid_t pgrp)
 {
 	struct task_struct *curr = current;
 
-	if (process_session(curr) != session) {
+	if (curr->session != session) {
 		detach_pid(curr, PIDTYPE_SID);
-		curr->signal->session = session;
+		curr->session = session;
 		attach_pid(curr, PIDTYPE_SID, session);
 	}
 	if (process_group(curr) != pgrp) {
 		detach_pid(curr, PIDTYPE_PGID);
-		curr->signal->pgrp = pgrp;
+		curr->group_leader->__pgrp = pgrp;
 		attach_pid(curr, PIDTYPE_PGID, pgrp);
 	}
 }
@@ -303,7 +303,7 @@ void daemonize(const char *name, ...)
 	exit_mm(current);
 
 	set_special_pids(1, 1);
-	current->signal->tty = NULL;
+	current->tty = NULL;
 
 	/* Block and flush all signals */
 	sigfillset(&blocked);
@@ -515,7 +515,7 @@ static inline void reparent_thread(task_t *p, task_t *father, int traced)
 	 * outside, so the child pgrp is now orphaned.
 	 */
 	if ((process_group(p) != process_group(father)) &&
-	    (process_session(p) == process_session(father))) {
+	    (p->session == father->session)) {
 		int pgrp = process_group(p);
 
 		if (will_become_orphaned_pgrp(pgrp, NULL) && has_stopped_jobs(pgrp)) {
@@ -625,7 +625,7 @@ static void exit_notify(struct task_struct *tsk)
 	t = tsk->real_parent;
 	
 	if ((process_group(t) != process_group(tsk)) &&
-	    (process_session(t) == process_session(tsk)) &&
+	    (t->session == tsk->session) &&
 	    will_become_orphaned_pgrp(process_group(tsk), tsk) &&
 	    has_stopped_jobs(process_group(tsk))) {
 		__kill_pg_info(SIGHUP, (void *)1, process_group(tsk));
@@ -720,7 +720,7 @@ NORET_TYPE void do_exit(long code)
 	exit_itimers(tsk);
 	exit_thread();
 
-	if (process_session_leader(tsk))
+	if (tsk->leader)
 		disassociate_ctty(1);
 
 	module_put(tsk->thread_info->exec_domain->module);

kernel/fork.c

@@ -743,12 +743,6 @@ static inline int copy_signal(unsigned long clone_flags, struct task_struct * ts
 	sig->curr_target = NULL;
 	init_sigpending(&sig->shared_pending);
 
-	sig->tty = process_tty(current);
-	sig->pgrp = process_group(current);
-	sig->session = process_session(current);
-	sig->leader = 0;	/* session leadership doesn't inherit */
-	sig->tty_old_pgrp = 0;
-
 	return 0;
 }
 
@@ -795,9 +789,7 @@ struct task_struct *copy_process(unsigned long clone_flags,
 	 * Thread groups must share signals as well, and detached threads
 	 * can only be started up within the thread group.
 	 */
-	if ((clone_flags & CLONE_THREAD) &&
-		(clone_flags & (CLONE_SIGHAND|CLONE_DETACHED)) !=
-			(CLONE_SIGHAND|CLONE_DETACHED))
+	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 		return ERR_PTR(-EINVAL);
 
 	/*
@@ -902,6 +894,8 @@ struct task_struct *copy_process(unsigned long clone_flags,
 	init_timer(&p->real_timer);
 	p->real_timer.data = (unsigned long) p;
 
+	p->leader = 0;		/* session leadership doesn't inherit */
+	p->tty_old_pgrp = 0;
 	p->utime = p->stime = 0;
 	p->cutime = p->cstime = 0;
 	p->array = NULL;
@@ -1046,7 +1040,7 @@ struct task_struct *copy_process(unsigned long clone_flags,
 	if (thread_group_leader(p)) {
 		attach_pid(p, PIDTYPE_TGID, p->tgid);
 		attach_pid(p, PIDTYPE_PGID, process_group(p));
-		attach_pid(p, PIDTYPE_SID, process_session(p));
+		attach_pid(p, PIDTYPE_SID, p->session);
 		if (p->pid)
 			__get_cpu_var(process_counts)++;
 	} else

kernel/pid.c

@@ -253,14 +253,14 @@ void switch_exec_pids(task_t *leader, task_t *thread)
 
 	attach_pid(thread, PIDTYPE_PID, thread->pid);
 	attach_pid(thread, PIDTYPE_TGID, thread->tgid);
-	attach_pid(thread, PIDTYPE_PGID, thread->signal->pgrp);
-	attach_pid(thread, PIDTYPE_SID, thread->signal->session);
+	attach_pid(thread, PIDTYPE_PGID, leader->__pgrp);
+	attach_pid(thread, PIDTYPE_SID, thread->session);
 	list_add_tail(&thread->tasks, &init_task.tasks);
 
 	attach_pid(leader, PIDTYPE_PID, leader->pid);
 	attach_pid(leader, PIDTYPE_TGID, leader->tgid);
-	attach_pid(leader, PIDTYPE_PGID, leader->signal->pgrp);
-	attach_pid(leader, PIDTYPE_SID, leader->signal->session);
+	attach_pid(leader, PIDTYPE_PGID, leader->__pgrp);
+	attach_pid(leader, PIDTYPE_SID, leader->session);
 }
 
 /*

kernel/signal.c

@@ -593,8 +593,7 @@ static int check_kill_permission(int sig, struct siginfo *info,
 	error = -EPERM;
 	if ((!info || ((unsigned long)info != 1 &&
 			(unsigned long)info != 2 && SI_FROMUSER(info)))
-	    && ((sig != SIGCONT) ||
-		(process_session(current) != process_session(t)))
+	    && ((sig != SIGCONT) || (current->session != t->session))
 	    && (current->euid ^ t->suid) && (current->euid ^ t->uid)
 	    && (current->uid ^ t->suid) && (current->uid ^ t->uid)
 	    && !capable(CAP_KILL))
@@ -1103,7 +1102,7 @@ kill_sl_info(int sig, struct siginfo *info, pid_t sid)
 	retval = -ESRCH;
 	read_lock(&tasklist_lock);
 	for_each_task_pid(sid, PIDTYPE_SID, p, l, pid) {
-		if (!process_session_leader(p))
+		if (!p->leader)
 			continue;
 		err = group_send_sig_info(sig, info, p);
 		if (retval)

kernel/sys.c

@@ -969,7 +969,7 @@ asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
 
 	if (p->parent == current || p->real_parent == current) {
 		err = -EPERM;
-		if (process_session(p) != process_session(current))
+		if (p->session != current->session)
 			goto out;
 		err = -EACCES;
 		if (p->did_exec)
@@ -981,7 +981,7 @@ asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
 	}
 
 	err = -EPERM;
-	if (process_session_leader(p))
+	if (p->leader)
 		goto out;
 
 	if (pgid != pid) {
@@ -990,7 +990,7 @@ asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
 		struct list_head *l;
 
 		for_each_task_pid(pgid, PIDTYPE_PGID, p, l, pid)
-			if (process_session(p) == process_session(current))
+			if (p->session == current->session)
 				goto ok_pgid;
 		goto out;
 	}
@@ -1002,7 +1002,7 @@ asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
 
 	if (process_group(p) != pgid) {
 		detach_pid(p, PIDTYPE_PGID);
-		p->signal->pgrp = pgid;
+		p->group_leader->__pgrp = pgid;
 		attach_pid(p, PIDTYPE_PGID, pgid);
 	}
 
@@ -1044,7 +1044,7 @@ asmlinkage long sys_getpgrp(void)
 asmlinkage long sys_getsid(pid_t pid)
 {
 	if (!pid) {
-		return process_session(current);
+		return current->session;
 	} else {
 		int retval;
 		struct task_struct *p;
@@ -1056,7 +1056,7 @@ asmlinkage long sys_getsid(pid_t pid)
 		if(p) {
 			retval = security_task_getsid(p);
 			if (!retval)
-				retval = process_session(p);
+				retval = p->session;
 		}
 		read_unlock(&tasklist_lock);
 		return retval;
@@ -1077,10 +1077,10 @@ asmlinkage long sys_setsid(void)
 	if (pid)
 		goto out;
 
-	current->signal->leader = 1;
+	current->leader = 1;
 	__set_special_pids(current->pid, current->pid);
-	current->signal->tty = NULL;
-	current->signal->tty_old_pgrp = 0;
+	current->tty = NULL;
+	current->tty_old_pgrp = 0;
 	err = process_group(current);
 out:
 	write_unlock_irq(&tasklist_lock);

net/ipv4/netfilter/ipt_owner.c

@@ -90,7 +90,7 @@ match_sid(const struct sk_buff *skb, pid_t sid)
 	read_lock(&tasklist_lock);
 	do_each_thread(g, p) {
 		struct files_struct *files;
-		if (process_session(p) != sid)
+		if (p->session != sid)
 			continue;
 
 		task_lock(p);

net/ipv6/netfilter/ip6t_owner.c

@@ -56,7 +56,7 @@ match_sid(const struct sk_buff *skb, pid_t sid)
 	read_lock(&tasklist_lock);
 	do_each_thread(g, p) {
 		struct files_struct *files;
-		if (process_session(p) != sid)
+		if (p->session != sid)
 			continue;
 
 		task_lock(p);