linux-kernel - [PATCH 2/5] cgroup: remove redundant get/put of task struct

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1324422873-31001-3-git-send-email-msb@chromium.org>
Date:	Tue, 20 Dec 2011 15:14:30 -0800
From:	Mandeep Singh Baines <msb@...omium.org>
To:	Tejun Heo <tj@...nel.org>, Li Zefan <lizf@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Mandeep Singh Baines <msb@...omium.org>, Tejun Heo <tj@...nel.org>,
	Li Zefan <lizf@...fujitsu.com>,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <paul@...lmenage.org>
Subject: [PATCH 2/5] cgroup: remove redundant get/put of task struct

threadgroup_lock() guarantees that the target threadgroup will
remain stable - no new task will be added, no new PF_EXITING
will be set and exec won't happen.

Signed-off-by: Mandeep Singh Baines <msb@...omium.org>
Cc: Tejun Heo <tj@...nel.org>
Cc: Li Zefan <lizf@...fujitsu.com>
Cc: containers@...ts.linux-foundation.org
Cc: cgroups@...r.kernel.org
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Paul Menage <paul@...lmenage.org>
---
 kernel/cgroup.c |   12 +-----------
 1 files changed, 1 insertions(+), 11 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 4166066..6649529 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2130,7 +2130,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
 
 		/* as per above, nr_threads may decrease, but not increase. */
 		BUG_ON(i >= group_size);
-		get_task_struct(tsk);
 		/*
 		 * saying GFP_ATOMIC has no effect here because we did prealloc
 		 * earlier, but it's good form to communicate our expectations.
@@ -2152,7 +2151,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
 	/* methods shouldn't be called if no task is actually migrating */
 	retval = 0;
 	if (!nr_migrating_tasks)
-		goto out_put_tasks;
+		goto out_free_group_list;
 
 	/*
 	 * step 1: check that we can legitimately attach to the cgroup.
@@ -2233,12 +2232,6 @@ out_cancel_attach:
 				ss->cancel_attach(ss, cgrp, &tset);
 		}
 	}
-out_put_tasks:
-	/* clean up the array of referenced threads in the group. */
-	for (i = 0; i < group_size; i++) {
-		tc = flex_array_get(group, i);
-		put_task_struct(tc->task);
-	}
 out_free_group_list:
 	flex_array_free(group);
 	return retval;
@@ -2287,14 +2280,12 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
 			cgroup_unlock();
 			return -EACCES;
 		}
-		get_task_struct(tsk);
 		rcu_read_unlock();
 	} else {
 		if (threadgroup)
 			tsk = current->group_leader;
 		else
 			tsk = current;
-		get_task_struct(tsk);
 	}
 
 	threadgroup_lock(tsk);
@@ -2306,7 +2297,6 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
 
 	threadgroup_unlock(tsk);
 
-	put_task_struct(tsk);
 	cgroup_unlock();
 	return ret;
 }
-- 
1.7.3.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/