[PATCH] pid: use struct pid for talking about process groups in exitc

Modify has_stopped_jobs and will_become_orphan_pgrp to use struct pid based
process groups.  This reduces the number of hash tables looks ups and paves
the way for multiple pid spaces.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.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>

kernel/exit.c

@@ -210,22 +210,22 @@ struct pid *session_of_pgrp(struct pid *pgrp)
  *
  * "I ask you, have you ever known what it is to be an orphan?"
  */
-static int will_become_orphaned_pgrp(int pgrp, struct task_struct *ignored_task)
+static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
 {
 	struct task_struct *p;
 	int ret = 1;
 
-	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
+	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 		if (p == ignored_task
 				|| p->exit_state
 				|| is_init(p->real_parent))
 			continue;
-		if (process_group(p->real_parent) != pgrp &&
-		    process_session(p->real_parent) == process_session(p)) {
+		if (task_pgrp(p->real_parent) != pgrp &&
+		    task_session(p->real_parent) == task_session(p)) {
 			ret = 0;
 			break;
 		}
-	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
+	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 	return ret;	/* (sighing) "Often!" */
 }
 
@@ -234,23 +234,23 @@ int is_orphaned_pgrp(int pgrp)
 	int retval;
 
 	read_lock(&tasklist_lock);
-	retval = will_become_orphaned_pgrp(pgrp, NULL);
+	retval = will_become_orphaned_pgrp(find_pid(pgrp), NULL);
 	read_unlock(&tasklist_lock);
 
 	return retval;
 }
 
-static int has_stopped_jobs(int pgrp)
+static int has_stopped_jobs(struct pid *pgrp)
 {
 	int retval = 0;
 	struct task_struct *p;
 
-	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
+	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 		if (p->state != TASK_STOPPED)
 			continue;
 		retval = 1;
 		break;
-	} while_each_task_pid(pgrp, PIDTYPE_PGID, p);
+	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 	return retval;
 }
 
@@ -648,14 +648,14 @@ reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
 	 * than we are, and it was the only connection
 	 * outside, so the child pgrp is now orphaned.
 	 */
-	if ((process_group(p) != process_group(father)) &&
-	    (process_session(p) == process_session(father))) {
-		int pgrp = process_group(p);
+	if ((task_pgrp(p) != task_pgrp(father)) &&
+	    (task_session(p) == task_session(father))) {
+		struct pid *pgrp = task_pgrp(p);
 
 		if (will_become_orphaned_pgrp(pgrp, NULL) &&
 		    has_stopped_jobs(pgrp)) {
-			__kill_pg_info(SIGHUP, SEND_SIG_PRIV, pgrp);
-			__kill_pg_info(SIGCONT, SEND_SIG_PRIV, pgrp);
+			__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
+			__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
 		}
 	}
 }
@@ -735,6 +735,7 @@ static void exit_notify(struct task_struct *tsk)
 	int state;
 	struct task_struct *t;
 	struct list_head ptrace_dead, *_p, *_n;
+	struct pid *pgrp;
 
 	if (signal_pending(tsk) && !(tsk->signal->flags & SIGNAL_GROUP_EXIT)
 	    && !thread_group_empty(tsk)) {
@@ -787,12 +788,13 @@ 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)) &&
-	    will_become_orphaned_pgrp(process_group(tsk), tsk) &&
-	    has_stopped_jobs(process_group(tsk))) {
-		__kill_pg_info(SIGHUP, SEND_SIG_PRIV, process_group(tsk));
-		__kill_pg_info(SIGCONT, SEND_SIG_PRIV, process_group(tsk));
+	pgrp = task_pgrp(tsk);
+	if ((task_pgrp(t) != pgrp) &&
+	    (task_session(t) != task_session(tsk)) &&
+	    will_become_orphaned_pgrp(pgrp, tsk) &&
+	    has_stopped_jobs(pgrp)) {
+		__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
+		__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
 	}
 
 	/* Let father know we died