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From: Yafang Shao <laoar.shao@gmail.com>
To: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com,
	andrii@kernel.org, martin.lau@linux.dev, song@kernel.org,
	yonghong.song@linux.dev, kpsingh@kernel.org, sdf@google.com,
	haoluo@google.com, jolsa@kernel.org, tj@kernel.org,
	lizefan.x@bytedance.com, hannes@cmpxchg.org,
	yosryahmed@google.com, mkoutny@suse.com, sinquersw@gmail.com
Cc: cgroups@vger.kernel.org, bpf@vger.kernel.org,
	Yafang Shao <laoar.shao@gmail.com>
Subject: [RFC PATCH bpf-next 1/8] cgroup: Don't have to hold cgroup_mutex in task_cgroup_from_root()
Date: Sat,  7 Oct 2023 14:02:57 +0000	[thread overview]
Message-ID: <20231007140304.4390-2-laoar.shao@gmail.com> (raw)
In-Reply-To: <20231007140304.4390-1-laoar.shao@gmail.com>

The task cannot modify cgroups if we have already acquired the
css_set_lock, thus eliminating the need to hold the cgroup_mutex. Following
this change, task_cgroup_from_root() can be employed in non-sleepable contexts.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 kernel/cgroup/cgroup.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 1fb7f562289d..bd1692f48be5 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -1453,7 +1453,7 @@ static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
 
 /*
  * Return the cgroup for "task" from the given hierarchy. Must be
- * called with cgroup_mutex and css_set_lock held.
+ * called with css_set_lock held.
  */
 struct cgroup *task_cgroup_from_root(struct task_struct *task,
 				     struct cgroup_root *root)
@@ -1462,7 +1462,8 @@ struct cgroup *task_cgroup_from_root(struct task_struct *task,
 	 * No need to lock the task - since we hold css_set_lock the
 	 * task can't change groups.
 	 */
-	return cset_cgroup_from_root(task_css_set(task), root);
+	lockdep_assert_held(&css_set_lock);
+	return __cset_cgroup_from_root(task_css_set(task), root);
 }
 
 /*
-- 
2.30.1 (Apple Git-130)


  reply	other threads:[~2023-10-07 14:03 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-07 14:02 [RFC PATCH bpf-next 0/8] bpf, cgroup: Add BPF support for cgroup1 hierarchy Yafang Shao
2023-10-07 14:02 ` Yafang Shao [this message]
2023-10-07 15:50   ` [RFC PATCH bpf-next 1/8] cgroup: Don't have to hold cgroup_mutex in task_cgroup_from_root() Tejun Heo
2023-10-08  2:32     ` Yafang Shao
2023-10-09 14:45   ` Michal Koutný
2023-10-10  3:58     ` Yafang Shao
2023-10-10  8:29       ` Michal Koutný
2023-10-10 11:58         ` Yafang Shao
2023-10-07 14:02 ` [RFC PATCH bpf-next 2/8] cgroup: Add new helpers for cgroup1 hierarchy Yafang Shao
2023-10-07 15:55   ` Tejun Heo
2023-10-08  2:36     ` Yafang Shao
2023-10-09 11:32   ` Michal Koutný
2023-10-09 13:10     ` Yafang Shao
2023-10-09 14:48       ` Michal Koutný
2023-10-10  3:59         ` Yafang Shao
2023-10-07 14:02 ` [RFC PATCH bpf-next 3/8] bpf: Add kfuncs " Yafang Shao
2023-10-07 15:57   ` Tejun Heo
2023-10-08  2:37     ` Yafang Shao
2023-10-07 14:03 ` [RFC PATCH bpf-next 4/8] selftests/bpf: Fix issues in setup_classid_environment() Yafang Shao
2023-10-07 14:03 ` [RFC PATCH bpf-next 5/8] selftests/bpf: Add parallel support for classid Yafang Shao
2023-10-07 14:03 ` [RFC PATCH bpf-next 6/8] selftests/bpf: Add a new cgroup helper get_classid_cgroup_id() Yafang Shao
2023-10-07 14:03 ` [RFC PATCH bpf-next 7/8] selftests/bpf: Add a new cgroup helper get_cgroup_hierarchy_id() Yafang Shao
2023-10-07 14:03 ` [RFC PATCH bpf-next 8/8] selftests/bpf: Add selftests for cgroup1 hierarchy Yafang Shao
2023-10-09 11:46 ` [RFC PATCH bpf-next 0/8] bpf, cgroup: Add BPF support " Michal Koutný
2023-10-09 13:11   ` Yafang Shao

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