From: Yafang Shao <laoar.shao@gmail.com>
To: Tejun Heo <tj@kernel.org>
Cc: 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, lizefan.x@bytedance.com,
hannes@cmpxchg.org, yosryahmed@google.com, mkoutny@suse.com,
sinquersw@gmail.com, cgroups@vger.kernel.org,
bpf@vger.kernel.org
Subject: Re: [RFC PATCH bpf-next v2 1/9] cgroup: Make operations on the cgroup root_list RCU safe
Date: Thu, 19 Oct 2023 14:38:52 +0800 [thread overview]
Message-ID: <CALOAHbAd2S--=72c2267Lrcj_czkitdG9j97pai2zGqdAskvQQ@mail.gmail.com> (raw)
In-Reply-To: <ZS-m3t-_daPzEsJL@slm.duckdns.org>
On Wed, Oct 18, 2023 at 5:35 PM Tejun Heo <tj@kernel.org> wrote:
>
> On Tue, Oct 17, 2023 at 12:45:38PM +0000, Yafang Shao wrote:
> > #define for_each_root(root) \
> > - list_for_each_entry((root), &cgroup_roots, root_list)
> > + list_for_each_entry_rcu((root), &cgroup_roots, root_list, \
> > + !lockdep_is_held(&cgroup_mutex))
>
> Shouldn't that be lockdep_is_held() without the leading negation?
right. will fix it.
>
> > @@ -1386,13 +1386,15 @@ static inline struct cgroup *__cset_cgroup_from_root(struct css_set *cset,
> > }
> > }
> >
> > - BUG_ON(!res_cgroup);
> > + WARN_ON_ONCE(!res_cgroup && lockdep_is_held(&cgroup_mutex));
>
> This doesn't work. lockdep_is_held() is always true if !PROVE_LOCKING.
will use mutex_is_locked() instead.
>
> > return res_cgroup;
> > }
> >
> > /*
> > * look up cgroup associated with current task's cgroup namespace on the
> > - * specified hierarchy
> > + * specified hierarchy. Umount synchronization is ensured via VFS layer,
> > + * so we don't have to hold cgroup_mutex to prevent the root from being
> > + * destroyed.
> > */
>
> Yeah, as Michal said, let's not do it this way.
sure, will do it.
--
Regards
Yafang
next prev parent reply other threads:[~2023-10-19 6:39 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-17 12:45 [RFC PATCH bpf-next v2 0/9] bpf, cgroup: Add BPF support for cgroup1 hierarchy Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 1/9] cgroup: Make operations on the cgroup root_list RCU safe Yafang Shao
2023-10-17 13:20 ` Michal Koutný
2023-10-18 2:51 ` Yafang Shao
2023-10-18 9:35 ` Tejun Heo
2023-10-19 6:38 ` Yafang Shao [this message]
2023-10-19 19:08 ` Tejun Heo
2023-10-19 19:43 ` Waiman Long
2023-10-20 9:36 ` Yafang Shao
2023-10-20 17:51 ` Tejun Heo
2023-10-22 9:32 ` Yafang Shao
2023-10-25 8:06 ` kernel test robot
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 2/9] cgroup: Eliminate the need for cgroup_mutex in proc_cgroup_show() Yafang Shao
2023-10-17 14:04 ` Michal Koutný
2023-10-18 3:12 ` Yafang Shao
2023-10-18 9:38 ` Tejun Heo
2023-10-19 6:39 ` Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 3/9] cgroup: Add a new helper for cgroup1 hierarchy Yafang Shao
2023-10-18 9:44 ` Tejun Heo
2023-10-19 6:41 ` Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 4/9] bpf: Add a new kfunc " Yafang Shao
2023-10-18 9:40 ` Tejun Heo
2023-10-19 6:40 ` Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 5/9] selftests/bpf: Fix issues in setup_classid_environment() Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 6/9] selftests/bpf: Add parallel support for classid Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 7/9] selftests/bpf: Add a new cgroup helper get_classid_cgroup_id() Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 8/9] selftests/bpf: Add a new cgroup helper get_cgroup_hierarchy_id() Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 9/9] selftests/bpf: Add selftests for cgroup1 hierarchy Yafang Shao
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