From: Boqun Feng <boqun@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Ingo Molnar" <mingo@kernel.org>, "Will Deacon" <will@kernel.org>,
"Boqun Feng" <boqun@kernel.org>,
"Waiman Long" <longman@redhat.com>, "Gary Guo" <gary@garyguo.net>,
"Alice Ryhl" <aliceryhl@google.com>,
"Lyude Paul" <lyude@redhat.com>,
"Daniel Almeida" <daniel.almeida@collabora.com>,
"Onur Özkan" <work@onurozkan.dev>,
"Miguel Ojeda" <ojeda@kernel.org>,
"Danilo Krummrich" <dakr@kernel.org>,
linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org,
"Shrikanth Hegde" <sshegde@linux.ibm.com>,
"Madhavan Srinivasan" <maddy@linux.ibm.com>,
"Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
Subject: [PATCH v5 12/18] arm64: sched/preempt: Enable HAS_SEPARATE_PREEMPT_RESCHED_BITS
Date: Fri, 7 Aug 2026 00:02:09 -0700 [thread overview]
Message-ID: <20260807070218.27144-13-boqun@kernel.org> (raw)
In-Reply-To: <20260807070218.27144-1-boqun@kernel.org>
Arm64 already uses 64-bit preempt count and the need reschedule bit is
maintained in a separate 32-bit word from the preempt count. Therefore
preempt count has enough bits to represent 16 levels of NMI nesting,
hence enable it for arm64. This saves a per-CPU variable and additional
instructions in the NMI path.
Signed-off-by: Boqun Feng <boqun@kernel.org>
---
arch/arm64/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b3afe0688919..349c3533cd1e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -247,6 +247,7 @@ config ARM64
select PCI_SYSCALL if PCI
select POWER_RESET
select POWER_SUPPLY
+ select HAS_SEPARATE_PREEMPT_RESCHED_BITS
select SPARSE_IRQ
select SWIOTLB
select SYSCTL_EXCEPTION_TRACE
--
2.50.1 (Apple Git-155)
next prev parent reply other threads:[~2026-08-07 7:02 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-07 7:01 [PATCH v5 00/18] Refcounted interrupt disable and SpinLockIrq for Rust Boqun Feng
2026-08-07 7:01 ` [PATCH v5 01/18] preempt: Track NMI nesting to separate per-CPU counter Boqun Feng
2026-08-07 7:01 ` [PATCH v5 02/18] preempt: Introduce HARDIRQ_DISABLE_BITS Boqun Feng
2026-08-07 7:02 ` [PATCH v5 03/18] preempt: Introduce __preempt_count_{sub,add}_return() Boqun Feng
2026-08-07 7:02 ` [PATCH v5 04/18] openrisc: Include <linux/cpumask.h> in smp.h Boqun Feng
2026-08-07 7:02 ` [PATCH v5 05/18] irq & spin_lock: Add counted interrupt disabling/enabling Boqun Feng
2026-08-07 7:02 ` [PATCH v5 06/18] irq: Add KUnit test for refcounted interrupt enable/disable Boqun Feng
2026-08-07 7:02 ` [PATCH v5 07/18] irq: Add max local_interrupt_disable() nesting level kunit test case Boqun Feng
2026-08-07 7:02 ` [PATCH v5 08/18] locking: Switch to _irq_{disable,enable}() variants in cleanup guards Boqun Feng
2026-08-07 7:02 ` [PATCH v5 09/18] sched: Remove the unused preempt_offset parameter of __cant_sleep() Boqun Feng
2026-08-07 7:02 ` [PATCH v5 10/18] sched: Avoid signed comparison of preempt_count() in __cant_migrate() Boqun Feng
2026-08-07 7:02 ` [PATCH v5 11/18] preempt: Introduce HAS_SEPARATE_PREEMPT_RESCHED_BITS Boqun Feng
2026-08-07 7:02 ` Boqun Feng [this message]
2026-08-07 7:02 ` [PATCH v5 13/18] s390/preempt: Enable HAS_SEPARATE_PREEMPT_RESCHED_BITS Boqun Feng
2026-08-07 7:02 ` [PATCH v5 14/18] rust: Introduce interrupt module Boqun Feng
2026-08-07 7:02 ` [PATCH v5 15/18] rust: helper: Add spin_{un,}lock_irq_{enable,disable}() helpers Boqun Feng
2026-08-07 7:02 ` [PATCH v5 16/18] rust: sync: Use super::* in spinlock.rs Boqun Feng
2026-08-07 7:02 ` [PATCH v5 17/18] rust: sync: Add SpinLockIrq Boqun Feng
2026-08-07 7:02 ` [PATCH v5 18/18] rust: sync: Introduce SpinLockIrq::lock_with() and friends Boqun Feng
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