From: Tejun Heo <tj@kernel.org>
To: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>, Hao Luo <haoluo@google.com>,
Zefan Li <lizefan.x@bytedance.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Shuah Khan <shuah@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Michal Hocko <mhocko@kernel.org>,
Stanislav Fomichev <sdf@google.com>,
David Rientjes <rientjes@google.com>,
Greg Thelen <gthelen@google.com>,
Shakeel Butt <shakeelb@google.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
Cgroups <cgroups@vger.kernel.org>
Subject: Re: [PATCH bpf-next v1 2/5] cgroup: bpf: add cgroup_rstat_updated() and cgroup_rstat_flush() kfuncs
Date: Fri, 20 May 2022 01:16:00 -1000 [thread overview]
Message-ID: <Yod4cN+HayIDhR/c@slm.duckdns.org> (raw)
In-Reply-To: <20220520093607.sadvim2igfde6x22@apollo.legion>
On Fri, May 20, 2022 at 03:06:07PM +0530, Kumar Kartikeya Dwivedi wrote:
> With static noinline, the compiler will optimize away the function. With global
> noinline, it can still optimize away the call site, but will keep the function
> definition, so attach works. Therefore __weak is needed to ensure call is still
> emitted. With GCC __attribute__((noipa)) might have been more appropritate, but
> LLVM doesn't support it, so __weak is the next best thing supported by both with
> the same side effect.
Ah, okay, so it's to prevent compiler from optimizing away call to a noop
function by telling it that we don't know what the function might eventually
be. Thanks for the explanation. Yosry, can you please add a comment
explaining what's going on?
Thanks.
--
tejun
next prev parent reply other threads:[~2022-05-20 11:16 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-20 1:21 [PATCH bpf-next v1 0/5] bpf: rstat: cgroup hierarchical stats Yosry Ahmed
2022-05-20 1:21 ` [PATCH bpf-next v1 1/5] cgroup: bpf: add a hook for bpf progs to attach to rstat flushing Yosry Ahmed
2022-05-21 11:16 ` kernel test robot
2022-05-21 11:26 ` kernel test robot
2022-05-21 11:26 ` kernel test robot
2022-05-20 1:21 ` [PATCH bpf-next v1 2/5] cgroup: bpf: add cgroup_rstat_updated() and cgroup_rstat_flush() kfuncs Yosry Ahmed
2022-05-20 7:24 ` Tejun Heo
2022-05-20 9:13 ` Yosry Ahmed
2022-05-20 9:36 ` Kumar Kartikeya Dwivedi
2022-05-20 11:16 ` Tejun Heo [this message]
2022-05-20 16:06 ` Yosry Ahmed
2022-05-20 15:14 ` Yonghong Song
2022-05-20 16:08 ` Yosry Ahmed
2022-05-20 16:16 ` Yonghong Song
2022-05-20 16:20 ` Yosry Ahmed
2022-05-21 11:47 ` kernel test robot
2022-05-20 1:21 ` [PATCH bpf-next v1 3/5] bpf: Introduce cgroup iter Yosry Ahmed
2022-05-20 7:41 ` Tejun Heo
2022-05-20 7:58 ` Yosry Ahmed
2022-05-20 8:11 ` Tejun Heo
2022-05-20 11:27 ` Tejun Heo
2022-05-20 16:29 ` Yonghong Song
2022-05-20 16:45 ` Tejun Heo
2022-05-20 19:42 ` Hao Luo
2022-05-20 21:18 ` Yosry Ahmed
2022-05-20 22:19 ` Alexei Starovoitov
2022-05-20 22:36 ` Yosry Ahmed
2022-05-20 22:57 ` Tejun Heo
2022-05-21 0:59 ` Yonghong Song
2022-05-21 2:34 ` Hao Luo
2022-05-23 23:58 ` Andrii Nakryiko
2022-05-24 0:53 ` Hao Luo
2022-05-24 1:30 ` Andrii Nakryiko
2022-05-20 21:49 ` Hao Luo
2022-05-21 0:58 ` Yonghong Song
2022-05-21 2:43 ` Hao Luo
2022-05-21 4:53 ` Tejun Heo
2022-05-21 0:52 ` Yonghong Song
2022-05-20 17:30 ` Hao Luo
2022-05-20 1:21 ` [PATCH bpf-next v1 4/5] selftests/bpf: extend cgroup helpers Yosry Ahmed
2022-05-20 1:21 ` [PATCH bpf-next v1 5/5] bpf: add a selftest for cgroup hierarchical stats collection Yosry Ahmed
2022-05-20 16:09 ` Yonghong Song
2022-05-20 16:18 ` Yosry Ahmed
2022-05-24 0:01 ` Andrii Nakryiko
2022-05-24 2:35 ` Yosry Ahmed
2022-06-03 16:23 ` Michal Koutný
2022-06-03 19:52 ` Yosry Ahmed
2022-06-06 12:32 ` Michal Koutný
2022-06-06 19:41 ` Yosry Ahmed
2022-06-07 12:12 ` Michal Koutný
2022-06-07 17:43 ` Yosry Ahmed
2022-06-08 11:17 ` Michal Koutný
2022-06-03 16:22 ` [PATCH bpf-next v1 0/5] bpf: rstat: cgroup hierarchical stats Michal Koutný
2022-06-03 19:47 ` Yosry Ahmed
2022-06-06 12:32 ` Michal Koutný
2022-06-06 19:32 ` Yosry Ahmed
2022-06-06 19:54 ` Kumar Kartikeya Dwivedi
2022-06-06 20:00 ` Yosry Ahmed
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