From: Waiman Long <longman@redhat.com>
To: Tejun Heo <tj@kernel.org>, Yafang Shao <laoar.shao@gmail.com>
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 15:43:26 -0400 [thread overview]
Message-ID: <09ff4166-bcc2-989b-97ce-a6574120eea7@redhat.com> (raw)
In-Reply-To: <ZTF-nOb4HDvjTSca@slm.duckdns.org>
On 10/19/23 15:08, Tejun Heo wrote:
> On Thu, Oct 19, 2023 at 02:38:52PM +0800, Yafang Shao wrote:
>>>> - 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.
> But then, someone else can hold the lock and trigger the condition
> spuriously. The kernel doesn't track who's holding the lock unless lockdep
> is enabled.
It is actually possible to detect if the current process is the owner of
a mutex since there is a owner field in the mutex structure. However,
the owner field also contains additional information which need to be
masked off before comparing with "current". If such a functionality is
really needed, we will have to add a helper function mutex_is_held(),
for example, to kernel/locking/mutex.c.
Cheers,
Longman
next prev parent reply other threads:[~2023-10-19 19:43 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
2023-10-19 19:08 ` Tejun Heo
2023-10-19 19:43 ` Waiman Long [this message]
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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