Refcounted interrupt disable and SpinLockIrq for rust (Part 1)
| From: | Boqun Feng <boqun-AT-kernel.org> | |
| To: | Peter Zijlstra <peterz-AT-infradead.org> | |
| Subject: | [PATCH v2 00/12] Refcounted interrupt disable and SpinLockIrq for rust (Part 1) | |
| Date: | Tue, 26 May 2026 08:21:36 -0700 | |
| Message-ID: | <20260526152148.30514-1-boqun@kernel.org> | |
| Cc: | Catalin Marinas <catalin.marinas-AT-arm.com>, Will Deacon <will-AT-kernel.org>, Jonas Bonn <jonas-AT-southpole.se>, Stefan Kristiansson <stefan.kristiansson-AT-saunalahti.fi>, Stafford Horne <shorne-AT-gmail.com>, Heiko Carstens <hca-AT-linux.ibm.com>, Vasily Gorbik <gor-AT-linux.ibm.com>, Alexander Gordeev <agordeev-AT-linux.ibm.com>, Christian Borntraeger <borntraeger-AT-linux.ibm.com>, Sven Schnelle <svens-AT-linux.ibm.com>, Thomas Gleixner <tglx-AT-kernel.org>, Ingo Molnar <mingo-AT-redhat.com>, Borislav Petkov <bp-AT-alien8.de>, Dave Hansen <dave.hansen-AT-linux.intel.com>, x86-AT-kernel.org, "H. Peter Anvin" <hpa-AT-zytor.com>, Arnd Bergmann <arnd-AT-arndb.de>, Juri Lelli <juri.lelli-AT-redhat.com>, Vincent Guittot <vincent.guittot-AT-linaro.org>, Dietmar Eggemann <dietmar.eggemann-AT-arm.com>, Steven Rostedt <rostedt-AT-goodmis.org>, Ben Segall <bsegall-AT-google.com>, Mel Gorman <mgorman-AT-suse.de>, Valentin Schneider <vschneid-AT-redhat.com>, K Prateek Nayak <kprateek.nayak-AT-amd.com>, Boqun Feng <boqun-AT-kernel.org>, Waiman Long <longman-AT-redhat.com>, Andrew Morton <akpm-AT-linux-foundation.org>, Andrii Nakryiko <andrii-AT-kernel.org>, Eduard Zingerman <eddyz87-AT-gmail.com>, Alexei Starovoitov <ast-AT-kernel.org>, Daniel Borkmann <daniel-AT-iogearbox.net>, Martin KaFai Lau <martin.lau-AT-linux.dev>, Kumar Kartikeya Dwivedi <memxor-AT-gmail.com>, Song Liu <song-AT-kernel.org>, Yonghong Song <yonghong.song-AT-linux.dev>, Jiri Olsa <jolsa-AT-kernel.org>, Shuah Khan <shuah-AT-kernel.org>, Miguel Ojeda <ojeda-AT-kernel.org>, Gary Guo <gary-AT-garyguo.net>, Björn Roy Baron <bjorn3_gh-AT-protonmail.com>, Benno Lossin <lossin-AT-kernel.org>, Andreas Hindborg <a.hindborg-AT-kernel.org>, Alice Ryhl <aliceryhl-AT-google.com>, Trevor Gross <tmgross-AT-umich.edu>, Danilo Krummrich <dakr-AT-kernel.org>, Jinjie Ruan <ruanjinjie-AT-huawei.com>, Lyude Paul <lyude-AT-redhat.com>, Thomas Huth <thuth-AT-redhat.com>, Sohil Mehta <sohil.mehta-AT-intel.com>, "Xin Li (Intel)" <xin-AT-zytor.com>, Pawan Gupta <pawan.kumar.gupta-AT-linux.intel.com>, Nikunj A Dadhania <nikunj-AT-amd.com>, Joel Fernandes <joelagnelf-AT-nvidia.com>, Andy Shevchenko <andriy.shevchenko-AT-linux.intel.com>, Randy Dunlap <rdunlap-AT-infradead.org>, Yury Norov <ynorov-AT-nvidia.com>, Sebastian Andrzej Siewior <bigeasy-AT-linutronix.de>, linux-kernel-AT-vger.kernel.org, linux-openrisc-AT-vger.kernel.org, linux-s390-AT-vger.kernel.org, linux-arch-AT-vger.kernel.org, bpf-AT-vger.kernel.org, linux-kselftest-AT-vger.kernel.org, rust-for-linux-AT-vger.kernel.org, Onur Özkan <work-AT-onurozkan.dev>, Daniel Almeida <daniel.almeida-AT-collabora.com> | |
| Archive-link: | Article |
Hi Peter, This is a follow-up for Lyude's work [1]. After learning the current preempt_count() usage and how ARM64 handle this, I came up with this series that could resolve your feedback [2]. The basic idea is based on: 1) preempt_count() previously already masks our NEED_RESCHED bit, so the effective bits is 31bits 2) with a 64bit preempt count implementation (as in your PREEMPT_LONG proposal), the effective bits that record "whether we CAN preempt or not" still fit in 32bit (i.e. an int) as a result, I don't think we need to change the existing preempt_count() API, but rather keep "32bit vs 64bit" as an implementation detail. This saves us the need to change the printk code for preempt_count(). v1: https://lore.kernel.org/rust-for-linux/20260508042111.243... Changes since v1: * Rename PREEMPT_COUNT_64BIT to HAS_SEPARATE_PREEMPT_RESCHED_BITS per Mark Rutland. * Add s390's support for HAS_SEPARATE_PREEMPT_RESCHED_BITS for Heiko Carstens, thank you! * Reorder patch #1 and #2 per Steven Rostedt. * Keep the NMI count warning per Steven Rostedt and Joel Fernandes. * Fix an race between interrupt disabling and softirq reported by sashiko (see the changes in __irq_exit_rcu()). * Add Context Analysis annotations for the newly introduced API. * Sync the preempt bits changes to BPF tests. I would like to target this changes for 7.2 if possible. [1]: https://lore.kernel.org/all/20260121223933.1568682-1-lyud... [2]: https://lore.kernel.org/all/20260204111234.GA3031506@nois... Regards, Boqun Boqun Feng (8): preempt: Introduce HARDIRQ_DISABLE_BITS preempt: Introduce __preempt_count_{sub, add}_return() irq & spin_lock: Add counted interrupt disabling/enabling locking: Switch to _irq_{disable,enable}() variants in cleanup guards sched: Remove the unused preempt_offset parameter of __cant_sleep() sched: Avoid signed comparison of preempt_count() in __cant_migrate() preempt: Introduce HAS_SEPARATE_PREEMPT_RESCHED_BITS arm64: sched/preempt: Enable HAS_SEPARATE_PREEMPT_RESCHED_BITS Heiko Carstens (1): s390/preempt: Enable HAS_SEPARATE_PREEMPT_RESCHED_BITS Joel Fernandes (1): preempt: Track NMI nesting to separate per-CPU counter Lyude Paul (2): openrisc: Include <linux/cpumask.h> in smp.h irq: Add KUnit test for refcounted interrupt enable/disable arch/arm64/Kconfig | 1 + arch/arm64/include/asm/preempt.h | 18 +++ arch/openrisc/include/asm/smp.h | 2 + arch/s390/Kconfig | 1 + arch/s390/include/asm/lowcore.h | 13 ++- arch/s390/include/asm/preempt.h | 49 ++++---- arch/x86/Kconfig | 1 + arch/x86/include/asm/preempt.h | 61 +++++++--- arch/x86/kernel/cpu/common.c | 2 +- include/asm-generic/preempt.h | 14 +++ include/linux/hardirq.h | 43 ++++++- include/linux/interrupt_rc.h | 65 +++++++++++ include/linux/kernel.h | 4 +- include/linux/preempt.h | 35 ++++-- include/linux/spinlock.h | 48 +++++--- include/linux/spinlock_api_smp.h | 41 +++++++ include/linux/spinlock_api_up.h | 16 +++ include/linux/spinlock_rt.h | 18 +++ kernel/Kconfig.preempt | 4 + kernel/irq/Makefile | 1 + kernel/irq/refcount_interrupt_test.c | 109 ++++++++++++++++++ kernel/locking/spinlock.c | 29 +++++ kernel/sched/core.c | 18 ++- kernel/softirq.c | 22 +++- lib/locking-selftest.c | 2 +- .../testing/selftests/bpf/bpf_experimental.h | 7 +- 26 files changed, 544 insertions(+), 80 deletions(-) create mode 100644 include/linux/interrupt_rc.h create mode 100644 kernel/irq/refcount_interrupt_test.c -- 2.50.1 (Apple Git-155)