From: Jakub Kicinski <kuba@kernel.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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 08:38:12 -0800 [thread overview]
Message-ID: <20240118083812.1b91ba88@kernel.org> (raw)
In-Reply-To: <20240118082754.9L_QFIgU@linutronix.de>
On Thu, 18 Jan 2024 09:27:54 +0100 Sebastian Andrzej Siewior wrote:
> 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.
So there's no way for a process to know on RT that someone with higher
prio is waiting for it to release its locks? :(
next prev parent reply other threads:[~2024-01-18 16:38 UTC|newest]
Thread overview: 64+ 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
2024-01-18 16:38 ` Jakub Kicinski [this message]
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
2023-12-15 17:07 ` [Intel-wired-lan] " Sebastian Andrzej Siewior
2023-12-16 4:53 ` kernel test robot
2023-12-16 4:53 ` [Intel-wired-lan] " kernel test robot
2023-12-19 0:01 ` Nathan Chancellor
2023-12-19 0:01 ` [Intel-wired-lan] " Nathan Chancellor
2023-12-19 16:55 ` Nick Desaulniers
2023-12-19 16:55 ` [Intel-wired-lan] " 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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