From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Jakub Kicinski <kuba@kernel.org>
Cc: "Toke Høiland-Jørgensen" <toke@redhat.com>,
"Alexei Starovoitov" <alexei.starovoitov@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
"Network Development" <netdev@vger.kernel.org>,
"David S. Miller" <davem@davemloft.net>,
"Boqun Feng" <boqun.feng@gmail.com>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Eric Dumazet" <edumazet@google.com>,
"Frederic Weisbecker" <frederic@kernel.org>,
"Ingo Molnar" <mingo@redhat.com>,
"Paolo Abeni" <pabeni@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Waiman Long" <longman@redhat.com>,
"Will Deacon" <will@kernel.org>,
"Alexei Starovoitov" <ast@kernel.org>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Cong Wang" <xiyou.wangcong@gmail.com>,
"Hao Luo" <haoluo@google.com>,
"Jamal Hadi Salim" <jhs@mojatatu.com>,
"Jesper Dangaard Brouer" <hawk@kernel.org>,
"Jiri Olsa" <jolsa@kernel.org>, "Jiri Pirko" <jiri@resnulli.us>,
"John Fastabend" <john.fastabend@gmail.com>,
"KP Singh" <kpsingh@kernel.org>,
"Martin KaFai Lau" <martin.lau@linux.dev>,
"Ronak Doshi" <doshir@vmware.com>, "Song Liu" <song@kernel.org>,
"Stanislav Fomichev" <sdf@google.com>,
"VMware PV-Drivers Reviewers" <pv-drivers@vmware.com>,
"Yonghong Song" <yonghong.song@linux.dev>,
bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH net-next 15/24] net: Use nested-BH locking for XDP redirect.
Date: Thu, 18 Jan 2024 09:27:54 +0100 [thread overview]
Message-ID: <20240118082754.9L_QFIgU@linutronix.de> (raw)
In-Reply-To: <20240117180447.2512335b@kernel.org>
On 2024-01-17 18:04:47 [-0800], Jakub Kicinski wrote:
> Oh, and I'm bringing it up here, because CONFIG_RT can throw
> in "need_resched()" into the napi_rx_has_budget(), obviously.
need_resched() does not work on PREEMPT_RT the way you think. This
context (the NAPI poll callback) is preemptible and (by default) runs at
SCHED_FIFO 50 (within a threaded IRQ) so a context switch can happen at
any time by a task with higher priority.
If threadA gets preempted and owns a lock that threadB, with higher
priority, wants then threadA will get back on CPU, inherit the priority
of the threadB and continue to run until it releases the lock.
If this is the per-CPU BH lock (which I want to remove) then it will
continue until all softirqs complete.
Sebastian
next prev parent reply other threads:[~2024-01-18 8:27 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-15 17:07 [PATCH net-next 00/24] locking: Introduce nested-BH locking Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 01/24] locking/local_lock: Introduce guard definition for local_lock Sebastian Andrzej Siewior
2023-12-18 8:16 ` Paolo Abeni
2024-01-11 16:19 ` Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 02/24] locking/local_lock: Add local nested BH locking infrastructure Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 03/24] net: Use __napi_alloc_frag_align() instead of open coding it Sebastian Andrzej Siewior
2023-12-18 7:48 ` Paolo Abeni
2024-01-12 9:01 ` Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 04/24] net: Use nested-BH locking for napi_alloc_cache Sebastian Andrzej Siewior
2023-12-16 4:43 ` kernel test robot
2024-01-12 10:58 ` Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 05/24] net/tcp_sigpool: Use nested-BH locking for sigpool_scratch Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 06/24] net/ipv4: Use nested-BH locking for ipv4_tcp_sk Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 07/24] netfilter: br_netfilter: Use nested-BH locking for brnf_frag_data_storage Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 08/24] net: softnet_data: Make xmit.recursion per task Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 09/24] dev: Use the RPS lock for softnet_data::input_pkt_queue on PREEMPT_RT Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 10/24] dev: Use nested-BH locking for softnet_data.process_queue Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 11/24] lwt: Don't disable migration prio invoking BPF Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 12/24] seg6: Use nested-BH locking for seg6_bpf_srh_states Sebastian Andrzej Siewior
2023-12-16 3:39 ` kernel test robot
2023-12-18 8:33 ` Paolo Abeni
2024-01-12 11:23 ` Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 13/24] net: Use nested-BH locking for bpf_scratchpad Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 14/24] net: Add a lock which held during the redirect process Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 15/24] net: Use nested-BH locking for XDP redirect Sebastian Andrzej Siewior
2023-12-16 4:12 ` kernel test robot
2023-12-20 0:25 ` Alexei Starovoitov
2024-01-04 19:29 ` Toke Høiland-Jørgensen
2024-01-12 17:41 ` Sebastian Andrzej Siewior
2024-01-17 16:37 ` Toke Høiland-Jørgensen
2024-01-18 2:04 ` Jakub Kicinski
2024-01-18 8:27 ` Sebastian Andrzej Siewior [this message]
2024-01-18 16:38 ` Jakub Kicinski
2024-01-18 16:50 ` Sebastian Andrzej Siewior
2024-01-18 11:51 ` Toke Høiland-Jørgensen
2024-01-18 16:37 ` Jakub Kicinski
2024-01-20 14:41 ` Toke Høiland-Jørgensen
2024-01-18 7:35 ` Sebastian Andrzej Siewior
2024-01-18 11:58 ` Toke Høiland-Jørgensen
2023-12-15 17:07 ` [PATCH net-next 16/24] net: netkit, veth, tun, virt*: " Sebastian Andrzej Siewior
2023-12-16 19:28 ` kernel test robot
2023-12-18 8:52 ` Daniel Borkmann
2024-01-12 15:37 ` Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 17/24] net: amazon, aquanti, broadcom, cavium, engleder: " Sebastian Andrzej Siewior
2023-12-16 22:09 ` Kiyanovski, Arthur
2024-01-12 17:53 ` Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 18/24] net: Freescale: " Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 19/24] net: fungible, gve, mtk, microchip, mana: " Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 20/24] net: intel: " Sebastian Andrzej Siewior
2023-12-16 4:53 ` kernel test robot
2023-12-19 0:01 ` Nathan Chancellor
2023-12-19 16:55 ` Nick Desaulniers
2023-12-15 17:07 ` [PATCH net-next 21/24] net: marvell: " Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 22/24] net: mellanox, nfp, sfc: " Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 23/24] net: qlogic, socionext, stmmac, cpsw: " Sebastian Andrzej Siewior
2023-12-15 17:07 ` [PATCH net-next 24/24] net: bpf: Add lockdep assert for the redirect process Sebastian Andrzej Siewior
2023-12-15 22:50 ` [PATCH net-next 00/24] locking: Introduce nested-BH locking Jakub Kicinski
2023-12-18 17:23 ` Sebastian Andrzej Siewior
2023-12-19 0:41 ` Jakub Kicinski
2023-12-21 20:46 ` Sebastian Andrzej Siewior
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