linux-kernel - [PATCH] sys_setpgid: eliminate unnecessary do_each_task_pid(PIDTYPE

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Message-ID: <20061023175152.GA115@oleg>
Date:	Mon, 23 Oct 2006 21:51:52 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...l.org>
Cc:	Cedric Le Goater <clg@...ibm.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Jeff Dike <jdike@...toit.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] sys_setpgid: eliminate unnecessary do_each_task_pid(PIDTYPE_PGID)

On top of add-process_session-helper-routine.patch

All tasks in the process group have the same sid, we don't need to iterate
them all to check that the caller of sys_setpgid() doesn't change its session.

Signed-off-by: Oleg Nesterov <oleg@...sign.ru>

--- rc2-mm2/kernel/sys.c~	2006-10-22 19:28:17.000000000 +0400
+++ rc2-mm2/kernel/sys.c	2006-10-23 20:35:56.000000000 +0400
@@ -1398,16 +1398,13 @@ asmlinkage long sys_setpgid(pid_t pid, p
 		goto out;
 
 	if (pgid != pid) {
-		struct task_struct *p;
+		struct task_struct *g =
+			find_task_by_pid_type(PIDTYPE_PGID, pgid);
 
-		do_each_task_pid(pgid, PIDTYPE_PGID, p) {
-			if (process_session(p) == process_session(group_leader))
-				goto ok_pgid;
-		} while_each_task_pid(pgid, PIDTYPE_PGID, p);
-		goto out;
+		if (!g || process_session(g) != process_session(group_leader))
+			goto out;
 	}
 
-ok_pgid:
 	err = security_task_setpgid(p, pgid);
 	if (err)
 		goto out;

-
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