From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Jesper Dangaard Brouer <hawk@kernel.org>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
"Björn Töpel" <bjorn@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
"Alexei Starovoitov" <ast@kernel.org>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Eric Dumazet" <edumazet@google.com>,
"Hao Luo" <haoluo@google.com>, "Jakub Kicinski" <kuba@kernel.org>,
"Jiri Olsa" <jolsa@kernel.org>,
"John Fastabend" <john.fastabend@gmail.com>,
"Jonathan Lemon" <jonathan.lemon@gmail.com>,
"KP Singh" <kpsingh@kernel.org>,
"Maciej Fijalkowski" <maciej.fijalkowski@intel.com>,
"Magnus Karlsson" <magnus.karlsson@intel.com>,
"Martin KaFai Lau" <martin.lau@linux.dev>,
"Paolo Abeni" <pabeni@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Song Liu" <song@kernel.org>,
"Stanislav Fomichev" <sdf@google.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Yonghong Song" <yonghong.song@linux.dev>
Subject: Re: [PATCH RFC net-next 1/2] net: Reference bpf_redirect_info via task_struct on PREEMPT_RT.
Date: Wed, 14 Feb 2024 14:23:10 +0100 [thread overview]
Message-ID: <87y1bndvsx.fsf@toke.dk> (raw)
In-Reply-To: <20240214121921.VJJ2bCBE@linutronix.de>
Sebastian Andrzej Siewior <bigeasy@linutronix.de> writes:
> On 2024-02-13 21:50:51 [+0100], Jesper Dangaard Brouer wrote:
>> I generally like the idea around bpf_xdp_storage.
>>
>> I only skimmed the code, but noticed some extra if-statements (for
>> !NULL). I don't think they will make a difference, but I know Toke want
>> me to test it...
>
> I've been looking at the assembly for the return value of
> bpf_redirect_info() and there is a NULL pointer check. I hoped it was
> obvious to be nun-NULL because it is a static struct.
>
> Should this become a problem I could add
> "__attribute__((returns_nonnull))" to the declaration of the function
> which will optimize the NULL check away.
If we know the function will never return NULL (I was wondering about
that, actually), why have the check in the C code at all? Couldn't we just
omit it entirely instead of relying on the compiler to optimise it out?
-Toke
next prev parent reply other threads:[~2024-02-14 13:23 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-13 14:58 [PATCH RFC net-next 0/2] Use per-task storage for XDP-redirects on PREEMPT_RT Sebastian Andrzej Siewior
2024-02-13 14:58 ` [PATCH RFC net-next 1/2] net: Reference bpf_redirect_info via task_struct " Sebastian Andrzej Siewior
2024-02-13 20:50 ` Jesper Dangaard Brouer
2024-02-14 12:19 ` Sebastian Andrzej Siewior
2024-02-14 13:23 ` Toke Høiland-Jørgensen [this message]
2024-02-14 14:28 ` Sebastian Andrzej Siewior
2024-02-14 16:08 ` Toke Høiland-Jørgensen
2024-02-14 16:36 ` Sebastian Andrzej Siewior
2024-02-15 20:23 ` Toke Høiland-Jørgensen
2024-02-16 16:57 ` Sebastian Andrzej Siewior
2024-02-19 19:01 ` Toke Høiland-Jørgensen
2024-02-20 9:17 ` Jesper Dangaard Brouer
2024-02-20 10:17 ` Sebastian Andrzej Siewior
2024-02-20 10:42 ` Jesper Dangaard Brouer
2024-02-20 12:08 ` Sebastian Andrzej Siewior
2024-02-20 12:57 ` Jesper Dangaard Brouer
2024-02-20 15:32 ` Sebastian Andrzej Siewior
2024-02-22 9:22 ` Sebastian Andrzej Siewior
2024-02-22 10:10 ` Jesper Dangaard Brouer
2024-02-22 10:58 ` Sebastian Andrzej Siewior
2024-02-20 12:10 ` Dave Taht
2024-02-14 16:13 ` Toke Høiland-Jørgensen
2024-02-15 9:04 ` Sebastian Andrzej Siewior
2024-02-15 12:11 ` Toke Høiland-Jørgensen
2024-02-13 14:58 ` [PATCH RFC net-next 2/2] net: Move per-CPU flush-lists to bpf_xdp_storage " Sebastian Andrzej Siewior
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