From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Yonghong Song <yhs@meta.com>
Cc: Yonghong Song <yhs@fb.com>, bpf <bpf@vger.kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Kernel Team <kernel-team@fb.com>,
Martin KaFai Lau <martin.lau@kernel.org>
Subject: Re: [PATCH bpf-next v10 3/4] bpf: Add kfunc bpf_rcu_read_lock/unlock()
Date: Fri, 25 Nov 2022 09:53:46 -0800 [thread overview]
Message-ID: <CAADnVQ+H3fm7ffLnJnG5DpKVaHDjPg2vEjRN0bPJOxqgMpKAFg@mail.gmail.com> (raw)
In-Reply-To: <540e410d-0a31-ac74-d258-a636530fd77b@meta.com>
On Thu, Nov 24, 2022 at 3:44 PM Yonghong Song <yhs@meta.com> wrote:
>
>
>
> On 11/24/22 12:34 PM, Alexei Starovoitov wrote:
> > On Wed, Nov 23, 2022 at 9:32 PM Yonghong Song <yhs@fb.com> wrote:
> >>
> >> @@ -16580,6 +16682,8 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr)
> >> env->bypass_spec_v1 = bpf_bypass_spec_v1();
> >> env->bypass_spec_v4 = bpf_bypass_spec_v4();
> >> env->bpf_capable = bpf_capable();
> >> + env->rcu_tag_supported =
> >> + btf_find_by_name_kind(btf_vmlinux, "rcu", BTF_KIND_TYPE_TAG) > 0;
> >
> > It needs btf_vmlinux != NULL check as well,
> > since we error earlier only on IS_ERR(btf_vmlinux).
> > btf_vmlinux can be NULL at this point when CONFIG_DEBUG_INFO_BTF is not set.
>
> I checked the code and it looks like btf_find_by_name_kind can handle
> btf_vmlinux = NULL properly. Consider this is a unlikely case so
> I did not add btf_vmlinux checking here.
Good point. You're right.
I got confused by the similar !btf check in bpf_find_btf_id().
There it looks to be necessary. Here it's indeed redundant.
Sorry about that.
next prev parent reply other threads:[~2022-11-25 17:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-24 5:32 [PATCH bpf-next v10 0/4] bpf: Add bpf_rcu_read_lock() support Yonghong Song
2022-11-24 5:32 ` [PATCH bpf-next v10 1/4] compiler_types: Define __rcu as __attribute__((btf_type_tag("rcu"))) Yonghong Song
2022-11-24 5:32 ` [PATCH bpf-next v10 2/4] bpf: Introduce might_sleep field in bpf_func_proto Yonghong Song
2022-11-24 5:32 ` [PATCH bpf-next v10 3/4] bpf: Add kfunc bpf_rcu_read_lock/unlock() Yonghong Song
2022-11-24 20:34 ` Alexei Starovoitov
2022-11-24 20:56 ` Alexei Starovoitov
2022-11-24 23:44 ` Yonghong Song
2022-11-25 17:53 ` Alexei Starovoitov [this message]
2022-11-24 5:32 ` [PATCH bpf-next v10 4/4] selftests/bpf: Add tests for bpf_rcu_read_lock() Yonghong Song
2022-11-24 21:10 ` [PATCH bpf-next v10 0/4] bpf: Add bpf_rcu_read_lock() support patchwork-bot+netdevbpf
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