[PATCH] Fix setpgid and threads

From: Jeremy Fitzhardinge <jeremy@goop.org>

I'm resending my patch to fix this problem.  To recap: every task_struct
has its own copy of the thread group's pgrp.  Only the thread group
leader is allowed to change the tgrp's pgrp, but it only updates its own
copy of pgrp, while all the other threads in the tgrp use the old value
they inherited on creation.

This patch simply updates all the other thread's pgrp when the tgrp
leader changes pgrp.  Ulrich has already expressed reservations about
this patch since it is (1) incomplete (it doesn't cover the case of
other ids which have similar problems), (2) racy (it doesn't synchronize
with other threads looking at the task pgrp, so they could see an
inconsistent view) and (3) slow (it takes linear time with respect to
the number of threads in the tgrp).

My reaction is that (1) it fixes the actual bug I'm encountering in a
real program.  (2) doesn't really matter for pgrp, since it is mostly an
issue with respect to the terminal job-control code (which is even more
broken without this patch.  Regarding (3), I think there are very few
programs which have a large number of threads which change process group
id on a regular basis (a heavily multi-threaded job-control shell?).

Ulrich also said he has a (proposed?) much better fix, which I've been
looking forward to.  I'm submitting this patch as a stop-gap fix for a
real bug, and perhaps to prompt the improved patch.

An alternative fix, at least for pgrp, is to change all references to
->pgrp to group_leader->pgrp.  This may be sufficient on its own, but it
would be a reasonably intrusive patch (I count 95 instances in 32 files
in the 2.6.0-test3-mm3 tree).

arch/h8300/kernel/signal.c

@@ -593,7 +593,7 @@ asmlinkage int do_signal(sigset_t *oldset, struct pt_regs *regs)
 				continue;
 
 			case SIGTSTP: case SIGTTIN: case SIGTTOU:
-				if (is_orphaned_pgrp(current->pgrp))
+				if (is_orphaned_pgrp(process_group(current)))
 					continue;
 				/* FALLTHRU */
 

arch/m68k/kernel/signal.c

@@ -1082,7 +1082,7 @@ asmlinkage int do_signal(sigset_t *oldset, struct pt_regs *regs)
 				continue;
 
 			case SIGTSTP: case SIGTTIN: case SIGTTOU:
-				if (is_orphaned_pgrp(current->pgrp))
+				if (is_orphaned_pgrp(process_group(current)))
 					continue;
 				/* FALLTHRU */
 

arch/m68knommu/kernel/signal.c

@@ -841,7 +841,7 @@ asmlinkage int do_signal(sigset_t *oldset, struct pt_regs *regs)
 				continue;
 
 			case SIGTSTP: case SIGTTIN: case SIGTTOU:
-				if (is_orphaned_pgrp(current->pgrp))
+				if (is_orphaned_pgrp(process_group(current)))
 					continue;
 				/* FALLTHRU */
 

arch/mips/kernel/irixelf.c

@@ -1130,7 +1130,7 @@ static int irix_core_dump(long signr, struct pt_regs * regs, struct file *file)
 	prstatus.pr_sighold = current->blocked.sig[0];
 	psinfo.pr_pid = prstatus.pr_pid = current->pid;
 	psinfo.pr_ppid = prstatus.pr_ppid = current->parent->pid;
-	psinfo.pr_pgrp = prstatus.pr_pgrp = current->pgrp;
+	psinfo.pr_pgrp = prstatus.pr_pgrp = process_group(current);
 	psinfo.pr_sid = prstatus.pr_sid = current->session;
 	prstatus.pr_utime.tv_sec = CT_TO_SECS(current->utime);
 	prstatus.pr_utime.tv_usec = CT_TO_USECS(current->utime);

arch/mips/kernel/irixsig.c

@@ -582,7 +582,7 @@ asmlinkage int irix_waitsys(int type, int pid, struct irix5_siginfo *info,
 		p = list_entry(_p,struct task_struct,sibling);
 		if ((type == P_PID) && p->pid != pid)
 			continue;
-		if ((type == P_PGID) && p->pgrp != pid)
+		if ((type == P_PGID) && process_group(p) != pid)
 			continue;
 		if ((p->exit_signal != SIGCHLD))
 			continue;

arch/mips/kernel/sysirix.c

@@ -803,11 +803,11 @@ asmlinkage int irix_setpgrp(int flags)
 	printk("[%s:%d] setpgrp(%d) ", current->comm, current->pid, flags);
 #endif
 	if(!flags)
-		error = current->pgrp;
+		error = process_group(current);
 	else
 		error = sys_setsid();
 #ifdef DEBUG_PROCGRPS
-	printk("returning %d\n", current->pgrp);
+	printk("returning %d\n", process_group(current));
 #endif
 
 	return error;

arch/sparc64/solaris/misc.c

@@ -392,7 +392,7 @@ asmlinkage int solaris_procids(int cmd, s32 pid, s32 pgid)
 	
 	switch (cmd) {
 	case 0: /* getpgrp */
-		return current->pgrp;
+		return process_group(current);
 	case 1: /* setpgrp */
 		{
 			int (*sys_setpgid)(pid_t,pid_t) =
@@ -403,7 +403,7 @@ asmlinkage int solaris_procids(int cmd, s32 pid, s32 pgid)
 			ret = sys_setpgid(0, 0);
 			if (ret) return ret;
 			current->tty = NULL;
-			return current->pgrp;
+			return process_group(current);
 		}
 	case 2: /* getsid */
 		{

drivers/char/n_tty.c

@@ -977,11 +977,11 @@ static ssize_t read_chan(struct tty_struct *tty, struct file *file,
 	if (file->f_op->write != redirected_tty_write && current->tty == tty) {
 		if (tty->pgrp <= 0)
 			printk("read_chan: tty->pgrp <= 0!\n");
-		else if (current->pgrp != tty->pgrp) {
+		else if (process_group(current) != tty->pgrp) {
 			if (is_ignored(SIGTTIN) ||
-			    is_orphaned_pgrp(current->pgrp))
+			    is_orphaned_pgrp(process_group(current)))
 				return -EIO;
-			kill_pg(current->pgrp, SIGTTIN, 1);
+			kill_pg(process_group(current), SIGTTIN, 1);
 			return -ERESTARTSYS;
 		}
 	}

drivers/char/rocket.c

@@ -956,7 +956,7 @@ 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 = current->session;
-	info->pgrp = current->pgrp;
+	info->pgrp = process_group(current);
 
 	if ((info->flags & ROCKET_INITIALIZED) == 0) {
 		cp = &info->channel;

drivers/char/tty_io.c

@@ -325,13 +325,13 @@ int tty_check_change(struct tty_struct * tty)
 		printk(KERN_WARNING "tty_check_change: tty->pgrp <= 0!\n");
 		return 0;
 	}
-	if (current->pgrp == tty->pgrp)
+	if (process_group(current) == tty->pgrp)
 		return 0;
 	if (is_ignored(SIGTTOU))
 		return 0;
-	if (is_orphaned_pgrp(current->pgrp))
+	if (is_orphaned_pgrp(process_group(current)))
 		return -EIO;
-	(void) kill_pg(current->pgrp,SIGTTOU,1);
+	(void) kill_pg(process_group(current), SIGTTOU, 1);
 	return -ERESTARTSYS;
 }
 
@@ -1406,7 +1406,7 @@ static int tty_open(struct inode * inode, struct file * filp)
 		task_unlock(current);
 		current->tty_old_pgrp = 0;
 		tty->session = current->session;
-		tty->pgrp = current->pgrp;
+		tty->pgrp = process_group(current);
 	}
 	return 0;
 }
@@ -1580,7 +1580,7 @@ static int tiocsctty(struct tty_struct *tty, int arg)
 	task_unlock(current);
 	current->tty_old_pgrp = 0;
 	tty->session = current->session;
-	tty->pgrp = current->pgrp;
+	tty->pgrp = process_group(current);
 	return 0;
 }
 

drivers/isdn/i4l/isdn_tty.c

@@ -1989,7 +1989,8 @@ modem_write_profile(atemu * m)
 	memcpy(m->pmsn, m->msn, ISDN_MSNLEN);
 	memcpy(m->plmsn, m->lmsn, ISDN_LMSNLEN);
 	if ((get_isdn_dev())->profd)
-		kill_pg_info(SIGIO, SEND_SIG_PRIV, (get_isdn_dev())->profd->pgrp);
+		kill_pg_info(SIGIO, SEND_SIG_PRIV,
+			process_group((get_isdn_dev())->profd));
 }
 
 static struct tty_operations modem_ops = {

fs/autofs/autofs_i.h

@@ -123,7 +123,7 @@ static inline struct autofs_sb_info *autofs_sbi(struct super_block *sb)
    filesystem without "magic".) */
 
 static inline int autofs_oz_mode(struct autofs_sb_info *sbi) {
-	return sbi->catatonic || current->pgrp == sbi->oz_pgrp;
+	return sbi->catatonic || process_group(current) == sbi->oz_pgrp;
 }
 
 /* Hash operations */

fs/autofs/inode.c

@@ -51,7 +51,7 @@ static int parse_options(char *options, int *pipefd, uid_t *uid, gid_t *gid, pid
 	
 	*uid = current->uid;
 	*gid = current->gid;
-	*pgrp = current->pgrp;
+	*pgrp = process_group(current);
 
 	*minproto = *maxproto = AUTOFS_PROTO_VERSION;
 
@@ -129,7 +129,7 @@ int autofs_fill_super(struct super_block *s, void *data, int silent)
 	sbi->magic = AUTOFS_SBI_MAGIC;
 	sbi->catatonic = 0;
 	sbi->exp_timeout = 0;
-	sbi->oz_pgrp = current->pgrp;
+	sbi->oz_pgrp = process_group(current);
 	autofs_initialize_hash(&sbi->dirhash);
 	sbi->queues = NULL;
 	memset(sbi->symlink_bitmap, 0, sizeof(long)*AUTOFS_SYMLINK_BITMAP_LEN);

fs/autofs/root.c

@@ -213,7 +213,7 @@ static struct dentry *autofs_root_lookup(struct inode *dir, struct dentry *dentr
 
 	oz_mode = autofs_oz_mode(sbi);
 	DPRINTK(("autofs_lookup: pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d\n",
-		 current->pid, current->pgrp, sbi->catatonic, oz_mode));
+		 current->pid, process_group(current), sbi->catatonic, oz_mode));
 
 	/*
 	 * Mark the dentry incomplete, but add it. This is needed so
@@ -527,7 +527,7 @@ static int autofs_root_ioctl(struct inode *inode, struct file *filp,
 {
 	struct autofs_sb_info *sbi = autofs_sbi(inode->i_sb);
 
-	DPRINTK(("autofs_ioctl: cmd = 0x%08x, arg = 0x%08lx, sbi = %p, pgrp = %u\n",cmd,arg,sbi,current->pgrp));
+	DPRINTK(("autofs_ioctl: cmd = 0x%08x, arg = 0x%08lx, sbi = %p, pgrp = %u\n",cmd,arg,sbi,process_group(current)));
 
 	if ( _IOC_TYPE(cmd) != _IOC_TYPE(AUTOFS_IOC_FIRST) ||
 	     _IOC_NR(cmd) - _IOC_NR(AUTOFS_IOC_FIRST) >= AUTOFS_IOC_COUNT )

fs/autofs4/autofs_i.h

@@ -113,7 +113,7 @@ static inline struct autofs_info *autofs4_dentry_ino(struct dentry *dentry)
    filesystem without "magic".) */
 
 static inline int autofs4_oz_mode(struct autofs_sb_info *sbi) {
-	return sbi->catatonic || current->pgrp == sbi->oz_pgrp;
+	return sbi->catatonic || process_group(current) == sbi->oz_pgrp;
 }
 
 /* Does a dentry have some pending activity? */

fs/autofs4/inode.c

@@ -101,7 +101,7 @@ static int parse_options(char *options, int *pipefd, uid_t *uid, gid_t *gid,
 	
 	*uid = current->uid;
 	*gid = current->gid;
-	*pgrp = current->pgrp;
+	*pgrp = process_group(current);
 
 	*minproto = AUTOFS_MIN_PROTO_VERSION;
 	*maxproto = AUTOFS_MAX_PROTO_VERSION;
@@ -192,7 +192,7 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent)
 	sbi->magic = AUTOFS_SBI_MAGIC;
 	sbi->catatonic = 0;
 	sbi->exp_timeout = 0;
-	sbi->oz_pgrp = current->pgrp;
+	sbi->oz_pgrp = process_group(current);
 	sbi->sb = s;
 	sbi->version = 0;
 	sbi->queues = NULL;

fs/autofs4/root.c

@@ -255,7 +255,7 @@ static struct dentry *autofs4_root_lookup(struct inode *dir, struct dentry *dent
 	lock_kernel();
 	oz_mode = autofs4_oz_mode(sbi);
 	DPRINTK(("autofs_lookup: pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d\n",
-		 current->pid, current->pgrp, sbi->catatonic, oz_mode));
+		 current->pid, process_group(current), sbi->catatonic, oz_mode));
 
 	/*
 	 * Mark the dentry incomplete, but add it. This is needed so
@@ -518,7 +518,7 @@ static int autofs4_root_ioctl(struct inode *inode, struct file *filp,
 	struct autofs_sb_info *sbi = autofs4_sbi(inode->i_sb);
 
 	DPRINTK(("autofs_ioctl: cmd = 0x%08x, arg = 0x%08lx, sbi = %p, pgrp = %u\n",
-		 cmd,arg,sbi,current->pgrp));
+		 cmd,arg,sbi,process_group(current)));
 
 	if ( _IOC_TYPE(cmd) != _IOC_TYPE(AUTOFS_IOC_FIRST) ||
 	     _IOC_NR(cmd) - _IOC_NR(AUTOFS_IOC_FIRST) >= AUTOFS_IOC_COUNT )

fs/binfmt_elf.c

@@ -1077,7 +1077,7 @@ static void fill_prstatus(struct elf_prstatus *prstatus,
 	prstatus->pr_sighold = p->blocked.sig[0];
 	prstatus->pr_pid = p->pid;
 	prstatus->pr_ppid = p->parent->pid;
-	prstatus->pr_pgrp = p->pgrp;
+	prstatus->pr_pgrp = process_group(p);
 	prstatus->pr_sid = p->session;
 	jiffies_to_timeval(p->utime, &prstatus->pr_utime);
 	jiffies_to_timeval(p->stime, &prstatus->pr_stime);
@@ -1105,7 +1105,7 @@ 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 = p->pgrp;
+	psinfo->pr_pgrp = process_group(p);
 	psinfo->pr_sid = p->session;
 
 	i = p->state ? ffz(~p->state) + 1 : 0;

fs/coda/upcall.c

@@ -54,7 +54,7 @@ static void *alloc_upcall(int opcode, int size)
 
         inp->ih.opcode = opcode;
 	inp->ih.pid = current->pid;
-	inp->ih.pgid = current->pgrp;
+	inp->ih.pgid = process_group(current);
 #ifdef CODA_FS_OLD_API
 	memset(&inp->ih.cred, 0, sizeof(struct coda_cred));
 	inp->ih.cred.cr_fsuid = current->fsuid;

fs/devfs/base.c

@@ -1334,7 +1334,7 @@ static int is_devfsd_or_child (struct fs_info *fs_info)
     struct task_struct *p = current;
 
     if (p == fs_info->devfsd_task) return (TRUE);
-    if (p->pgrp == fs_info->devfsd_pgrp) return (TRUE);
+    if (process_group(p) == fs_info->devfsd_pgrp) return (TRUE);
     read_lock(&tasklist_lock);
     for ( ; p != &init_task; p = p->real_parent)
     {
@@ -2744,8 +2744,8 @@ static int devfsd_ioctl (struct inode *inode, struct file *file,
 	    }
 	    fs_info->devfsd_task = current;
 	    spin_unlock (&lock);
-	    fs_info->devfsd_pgrp = (current->pgrp == current->pid) ?
-		current->pgrp : 0;
+	    fs_info->devfsd_pgrp = (process_group(current) == current->pid) ?
+		process_group(current) : 0;
 	    fs_info->devfsd_file = file;
 	    fs_info->devfsd_info = kmalloc (sizeof *fs_info->devfsd_info,
 					    GFP_KERNEL);

fs/proc/array.c

@@ -341,7 +341,7 @@ int proc_pid_stat(struct task_struct *task, char * buffer)
 		task->comm,
 		state,
 		ppid,
-		task->pgrp,
+		process_group(task),
 		task->session,
 		tty_nr,
 		tty_pgrp,

include/linux/sched.h

@@ -362,7 +362,7 @@ struct task_struct {
 	unsigned long personality;
 	int did_exec:1;
 	pid_t pid;
-	pid_t pgrp;
+	pid_t __pgrp;		/* Accessed via process_group() */
 	pid_t tty_old_pgrp;
 	pid_t session;
 	pid_t tgid;
@@ -377,7 +377,7 @@ struct task_struct {
 	struct task_struct *parent;	/* parent process */
 	struct list_head children;	/* list of my children */
 	struct list_head sibling;	/* linkage in my parent's children list */
-	struct task_struct *group_leader;
+	struct task_struct *group_leader;	/* threadgroup leader */
 
 	/* PID/PID hash table linkage. */
 	struct pid_link pids[PIDTYPE_MAX];
@@ -463,6 +463,11 @@ struct task_struct {
 	siginfo_t *last_siginfo; /* For ptrace use.  */
 };
 
+static inline pid_t process_group(struct task_struct *tsk)
+{
+	return tsk->group_leader->__pgrp;
+}
+
 extern void __put_task_struct(struct task_struct *tsk);
 #define get_task_struct(tsk) do { atomic_inc(&(tsk)->usage); } while(0)
 #define put_task_struct(tsk) \

kernel/exit.c

@@ -152,7 +152,7 @@ static int will_become_orphaned_pgrp(int pgrp, task_t *ignored_task)
 				|| p->state >= TASK_ZOMBIE 
 				|| p->real_parent->pid == 1)
 			continue;
-		if (p->real_parent->pgrp != pgrp
+		if (process_group(p->real_parent) != pgrp
 			    && p->real_parent->session == p->session) {
 			ret = 0;
 			break;
@@ -247,9 +247,9 @@ void __set_special_pids(pid_t session, pid_t pgrp)
 		curr->session = session;
 		attach_pid(curr, PIDTYPE_SID, session);
 	}
-	if (curr->pgrp != pgrp) {
+	if (process_group(curr) != pgrp) {
 		detach_pid(curr, PIDTYPE_PGID);
-		curr->pgrp = pgrp;
+		curr->group_leader->__pgrp = pgrp;
 		attach_pid(curr, PIDTYPE_PGID, pgrp);
 	}
 }
@@ -508,9 +508,9 @@ static inline void reparent_thread(task_t *p, task_t *father, int traced)
 	 * than we are, and it was the only connection
 	 * outside, so the child pgrp is now orphaned.
 	 */
-	if ((p->pgrp != father->pgrp) &&
+	if ((process_group(p) != process_group(father)) &&
 	    (p->session == father->session)) {
-		int pgrp = p->pgrp;
+		int pgrp = process_group(p);
 
 		if (will_become_orphaned_pgrp(pgrp, NULL) && has_stopped_jobs(pgrp)) {
 			__kill_pg_info(SIGHUP, (void *)1, pgrp);
@@ -618,12 +618,12 @@ static void exit_notify(struct task_struct *tsk)
 	 
 	t = tsk->real_parent;
 	
-	if ((t->pgrp != tsk->pgrp) &&
+	if ((process_group(t) != process_group(tsk)) &&
 	    (t->session == tsk->session) &&
-	    will_become_orphaned_pgrp(tsk->pgrp, tsk) &&
-	    has_stopped_jobs(tsk->pgrp)) {
-		__kill_pg_info(SIGHUP, (void *)1, tsk->pgrp);
-		__kill_pg_info(SIGCONT, (void *)1, tsk->pgrp);
+	    will_become_orphaned_pgrp(process_group(tsk), tsk) &&
+	    has_stopped_jobs(process_group(tsk))) {
+		__kill_pg_info(SIGHUP, (void *)1, process_group(tsk));
+		__kill_pg_info(SIGCONT, (void *)1, process_group(tsk));
 	}
 
 	/* Let father know we died 
@@ -813,10 +813,10 @@ static int eligible_child(pid_t pid, int options, task_t *p)
 		if (p->pid != pid)
 			return 0;
 	} else if (!pid) {
-		if (p->pgrp != current->pgrp)
+		if (process_group(p) != process_group(current))
 			return 0;
 	} else if (pid != -1) {
-		if (p->pgrp != -pid)
+		if (process_group(p) != -pid)
 			return 0;
 	}
 

kernel/fork.c

@@ -1004,7 +1004,7 @@ struct task_struct *copy_process(unsigned long clone_flags,
 	attach_pid(p, PIDTYPE_PID, p->pid);
 	if (thread_group_leader(p)) {
 		attach_pid(p, PIDTYPE_TGID, p->tgid);
-		attach_pid(p, PIDTYPE_PGID, p->pgrp);
+		attach_pid(p, PIDTYPE_PGID, process_group(p));
 		attach_pid(p, PIDTYPE_SID, p->session);
 		if (p->pid)
 			__get_cpu_var(process_counts)++;

kernel/pid.c

@@ -250,13 +250,13 @@ 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->pgrp);
+	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->pgrp);
+	attach_pid(leader, PIDTYPE_PGID, leader->__pgrp);
 	attach_pid(leader, PIDTYPE_SID, leader->session);
 }
 

kernel/signal.c

@@ -1139,7 +1139,7 @@ kill_proc_info(int sig, struct siginfo *info, pid_t pid)
 static int kill_something_info(int sig, struct siginfo *info, int pid)
 {
 	if (!pid) {
-		return kill_pg_info(sig, info, current->pgrp);
+		return kill_pg_info(sig, info, process_group(current));
 	} else if (pid == -1) {
 		int retval = 0, count = 0;
 		struct task_struct * p;
@@ -1798,7 +1798,7 @@ int get_signal_to_deliver(siginfo_t *info, struct pt_regs *regs, void *cookie)
 
 			/* signals can be posted during this window */
 
-			if (is_orphaned_pgrp(current->pgrp))
+			if (is_orphaned_pgrp(process_group(current)))
 				goto relock;
 
 			spin_lock_irq(&current->sighand->siglock);

kernel/sys.c

@@ -290,7 +290,7 @@ asmlinkage long sys_setpriority(int which, int who, int niceval)
 			break;
 		case PRIO_PGRP:
 			if (!who)
-				who = current->pgrp;
+				who = process_group(current);
 			for_each_task_pid(who, PIDTYPE_PGID, p, l, pid)
 				error = set_one_prio(p, niceval, error);
 			break;
@@ -346,7 +346,7 @@ asmlinkage long sys_getpriority(int which, int who)
 			break;
 		case PRIO_PGRP:
 			if (!who)
-				who = current->pgrp;
+				who = process_group(current);
 			for_each_task_pid(who, PIDTYPE_PGID, p, l, pid) {
 				niceval = 20 - task_nice(p);
 				if (niceval > retval)
@@ -979,11 +979,12 @@ asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
 	if (err)
 		goto out;
 
-	if (p->pgrp != pgid) {
+	if (process_group(p) != pgid) {
 		detach_pid(p, PIDTYPE_PGID);
-		p->pgrp = pgid;
+		p->group_leader->__pgrp = pgid;
 		attach_pid(p, PIDTYPE_PGID, pgid);
 	}
+
 	err = 0;
 out:
 	/* All paths lead to here, thus we are safe. -DaveM */
@@ -994,7 +995,7 @@ asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
 asmlinkage long sys_getpgid(pid_t pid)
 {
 	if (!pid) {
-		return current->pgrp;
+		return process_group(current);
 	} else {
 		int retval;
 		struct task_struct *p;
@@ -1006,7 +1007,7 @@ asmlinkage long sys_getpgid(pid_t pid)
 		if (p) {
 			retval = security_task_getpgid(p);
 			if (!retval)
-				retval = p->pgrp;
+				retval = process_group(p);
 		}
 		read_unlock(&tasklist_lock);
 		return retval;
@@ -1016,7 +1017,7 @@ asmlinkage long sys_getpgid(pid_t pid)
 asmlinkage long sys_getpgrp(void)
 {
 	/* SMP - assuming writes are word atomic this is fine */
-	return current->pgrp;
+	return process_group(current);
 }
 
 asmlinkage long sys_getsid(pid_t pid)
@@ -1059,7 +1060,7 @@ asmlinkage long sys_setsid(void)
 	__set_special_pids(current->pid, current->pid);
 	current->tty = NULL;
 	current->tty_old_pgrp = 0;
-	err = current->pgrp;
+	err = process_group(current);
 out:
 	write_unlock_irq(&tasklist_lock);
 	return err;