linux-kernel - [PATCH 5.4 269/434] cgroup: freezer: dont change task and cgroups status unnecessarily

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]

Date:   Sun, 29 Dec 2019 18:25:22 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Honglei Wang <honglei.wang@...cle.com>,
        Roman Gushchin <guro@...com>, Tejun Heo <tj@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 269/434] cgroup: freezer: dont change task and cgroups status unnecessarily

From: Honglei Wang <honglei.wang@...cle.com>

[ Upstream commit 742e8cd3e1ba6f19cad6d912f8d469df5557d0fd ]

It's not necessary to adjust the task state and revisit the state
of source and destination cgroups if the cgroups are not in freeze
state and the task itself is not frozen.

And in this scenario, it wakes up the task who's not supposed to be
ready to run.

Don't do the unnecessary task state adjustment can help stop waking
up the task without a reason.

Signed-off-by: Honglei Wang <honglei.wang@...cle.com>
Acked-by: Roman Gushchin <guro@...com>
Signed-off-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/cgroup/freezer.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/cgroup/freezer.c b/kernel/cgroup/freezer.c
index 8cf010680678..3984dd6b8ddb 100644
--- a/kernel/cgroup/freezer.c
+++ b/kernel/cgroup/freezer.c
@@ -230,6 +230,15 @@ void cgroup_freezer_migrate_task(struct task_struct *task,
 	if (task->flags & PF_KTHREAD)
 		return;
 
+	/*
+	 * It's not necessary to do changes if both of the src and dst cgroups
+	 * are not freezing and task is not frozen.
+	 */
+	if (!test_bit(CGRP_FREEZE, &src->flags) &&
+	    !test_bit(CGRP_FREEZE, &dst->flags) &&
+	    !task->frozen)
+		return;
+
 	/*
 	 * Adjust counters of freezing and frozen tasks.
 	 * Note, that if the task is frozen, but the destination cgroup is not
-- 
2.20.1