From: KP Singh <kpsingh@chromium.org>
To: Martin KaFai Lau <kafai@fb.com>
Cc: open list <linux-kernel@vger.kernel.org>,
bpf <bpf@vger.kernel.org>, Song Liu <songliubraving@fb.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Paul Turner <pjt@google.com>, Jann Horn <jannh@google.com>,
Hao Luo <haoluo@google.com>
Subject: Re: [PATCH bpf-next v3 1/9] bpf: Implement task local storage
Date: Wed, 4 Nov 2020 23:54:09 +0100 [thread overview]
Message-ID: <CACYkzJ6t12AORyTzAP_P3bZG-_K_01h7DVaUmYTWCd-8U-8-bQ@mail.gmail.com> (raw)
In-Reply-To: <20201104221526.dv6qfpfp5lk2t7zw@kafai-mbp.dhcp.thefacebook.com>
> > + WARN_ON_ONCE(!rcu_read_lock_held());
> > + task = pid_task(pid, PIDTYPE_PID);
> > + if (!task) {
> > + err = -ENOENT;
> > + goto out;
> > + }
> > +
> > + sdata = bpf_local_storage_update(
> > + task, (struct bpf_local_storage_map *)map, value, map_flags);
> It seems the task is protected by rcu here and the task may be going away.
> Is it ok?
>
> or the following comment in the later "BPF_CALL_4(bpf_task_storage_get, ...)"
> is no longer valid?
> /* This helper must only called from where the task is guaranteed
> * to have a refcount and cannot be freed.
> */
I reworded this (and the other similar comment) as:
/* This helper must only be called from places where the lifetime of the task
* is guaranteed. Either by being refcounted or by being protected
* by an RCU read-side critical section.
*/
next prev parent reply other threads:[~2020-11-04 22:54 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-04 16:44 [PATCH bpf-next v3 0/9] Implement task_local_storage KP Singh
2020-11-04 16:44 ` [PATCH bpf-next v3 1/9] bpf: Implement task local storage KP Singh
2020-11-04 22:08 ` Martin KaFai Lau
2020-11-04 22:17 ` Martin KaFai Lau
2020-11-04 22:15 ` Martin KaFai Lau
2020-11-04 22:54 ` KP Singh [this message]
2020-11-04 16:44 ` [PATCH bpf-next v3 2/9] libbpf: Add support for " KP Singh
2020-11-04 22:20 ` Martin KaFai Lau
2020-11-04 16:44 ` [PATCH bpf-next v3 3/9] bpftool: " KP Singh
2020-11-04 16:44 ` [PATCH bpf-next v3 4/9] bpf: Implement get_current_task_btf and RET_PTR_TO_BTF_ID KP Singh
2020-11-04 16:44 ` [PATCH bpf-next v3 5/9] bpf: Allow LSM programs to use bpf spin locks KP Singh
2020-11-04 22:35 ` Martin KaFai Lau
2020-11-04 22:44 ` KP Singh
2020-11-04 16:44 ` [PATCH bpf-next v3 6/9] bpf: Fix tests for local_storage KP Singh
2020-11-04 16:44 ` [PATCH bpf-next v3 7/9] bpf: Update selftests for local_storage to use vmlinux.h KP Singh
2020-11-04 16:44 ` [PATCH bpf-next v3 8/9] bpf: Add tests for task_local_storage KP Singh
2020-11-04 16:44 ` [PATCH bpf-next v3 9/9] bpf: Exercise syscall operations for inode and sk storage KP Singh
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