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Wed, 14 Feb 2024 05:23:10 -0800 (PST) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 9728310F57A4; Wed, 14 Feb 2024 14:23:10 +0100 (CET) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Sebastian Andrzej Siewior , Jesper Dangaard Brouer Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, =?utf-8?B?QmrDtnJuIFQ=?= =?utf-8?B?w7ZwZWw=?= , "David S. Miller" , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eric Dumazet , Hao Luo , Jakub Kicinski , Jiri Olsa , John Fastabend , Jonathan Lemon , KP Singh , Maciej Fijalkowski , Magnus Karlsson , Martin KaFai Lau , Paolo Abeni , Peter Zijlstra , Song Liu , Stanislav Fomichev , Thomas Gleixner , Yonghong Song Subject: Re: [PATCH RFC net-next 1/2] net: Reference bpf_redirect_info via task_struct on PREEMPT_RT. In-Reply-To: <20240214121921.VJJ2bCBE@linutronix.de> References: <20240213145923.2552753-1-bigeasy@linutronix.de> <20240213145923.2552753-2-bigeasy@linutronix.de> <66d9ee60-fbe3-4444-b98d-887845d4c187@kernel.org> <20240214121921.VJJ2bCBE@linutronix.de> X-Clacks-Overhead: GNU Terry Pratchett Date: Wed, 14 Feb 2024 14:23:10 +0100 Message-ID: <87y1bndvsx.fsf@toke.dk> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Sebastian Andrzej Siewior 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