[PATCH RFC v2 00/15] rcu-tasks: let preemption outside trampolines be a quiescent state · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
[PATCH RFC v2 01/15] rcu-tasks: Add per-task trampoline nesting count · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
Re: [PATCH RFC v2 01/15] rcu-tasks: Add per-task trampoline nesting count · "Paul E. McKenney" <paulmck@kernel.org> · 2026-09-11
[PATCH RFC v2 02/15] entry: Pass pt_regs to irqentry_exit_cond_resched() · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
[PATCH RFC v2 03/15] rcu-tasks: Hold trampoline nesting across irq-exit preemption in trampoline text · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
Re: [PATCH RFC v2 03/15] rcu-tasks: Hold trampoline nesting across irq-exit preemption in trampoline text · Frederic Weisbecker <frederic@kernel.org> · 2026-09-15
[PATCH RFC v2 04/15] kprobes: Let Tasks RCU recognise tasks preempted in an optprobe jump window · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
[PATCH RFC v2 05/15] ftrace: Mark modules hosting direct-call trampolines for Tasks RCU · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
[PATCH RFC v2 06/15] x86/ftrace: Maintain Tasks RCU trampoline nesting in ftrace_caller · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
[PATCH RFC v2 07/15] x86/kprobes: Maintain Tasks RCU trampoline nesting in the optprobe template · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
[PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · Alexei Starovoitov <hidden> · 2026-09-12
Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · "Paul E. McKenney" <paulmck@kernel.org> · 2026-09-12
Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · Alexei Starovoitov <hidden> · 2026-09-12
Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · "Paul E. McKenney" <paulmck@kernel.org> · 2026-09-12
Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · Alexei Starovoitov <hidden> · 2026-09-12
Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · "Paul E. McKenney" <paulmck@kernel.org> · 2026-09-12
Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · Alexei Starovoitov <hidden> · 2026-09-12
Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · "Paul E. McKenney" <paulmck@kernel.org> · 2026-09-13
Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · David Laight <hidden> · 2026-09-12
Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · "Paul E. McKenney" <paulmck@kernel.org> · 2026-09-12
Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · David Laight <hidden> · 2026-09-13
Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline · "Paul E. McKenney" <paulmck@kernel.org> · 2026-09-13
[PATCH RFC v2 09/15] arm64: ftrace: Maintain Tasks RCU trampoline nesting in ftrace_caller · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
[PATCH RFC v2 10/15] bpf, arm64: Maintain Tasks RCU trampoline nesting in the BPF trampoline · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
[PATCH RFC v2 11/15] samples: ftrace: Maintain Tasks RCU trampoline nesting in direct-call trampolines · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
[PATCH RFC v2 12/15] rcutorture: Bracket Tasks RCU readers with trampoline nesting · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
[PATCH RFC v2 13/15] rcu-tasks: Treat preemption outside trampolines as a quiescent state · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
[PATCH RFC v2 14/15] rcu-tasks: Retire switched-out tasks with no trampoline nesting at scan time · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
[PATCH RFC v2 15/15] rcu-tasks: Kick running holdouts through the scheduler · Josef Bacik <josef@toxicpanda.com> · 2026-09-11
Re: [PATCH RFC v2 15/15] rcu-tasks: Kick running holdouts through the scheduler · "Paul E. McKenney" <paulmck@kernel.org> · 2026-09-11
Re: [PATCH RFC v2 00/15] rcu-tasks: let preemption outside trampolines be a quiescent state · Yafang Shao <hidden> · 2026-09-13

Re: [PATCH RFC v2 08/15] bpf, x86: Maintain Tasks RCU trampoline nesting in the BPF trampoline

From: David Laight <hidden>
Date: 2026-09-12 21:14:03
Also in: bpf, linux-trace-kernel, lkml, rcu, xen-devel

On Sat, 12 Sep 2026 11:03:34 -0700
"Paul E. McKenney" [off-list ref] wrote:

In the old kernels, yes, we have current->trc_reader_nesting++.
In the newer kernels, Tasks Trace RCU is instead implemented in terms
of SRCU-fast, which instead increments per-CPU counters.  Which among
other thins is a bit faster and does not need to hook into the scheduler.

Isn't that rather architecture dependant?
It is fine on x86, but on arm incrementing a per-cpu variable is
significantly expensive.

David

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