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: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20231215171020.687342-1-bigeasy@linutronix.de>
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
2023-12-20 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
2023-12-18 8:52 ` Daniel Borkmann
2024-01-12 15:37 ` 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
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