From: Peter Zijlstra <peterz@infradead.org>
To: Boqun Feng <boqun@kernel.org>
Cc: "Shrikanth Hegde" <sshegde@linux.ibm.com>,
"Ingo Molnar" <mingo@kernel.org>, "Will Deacon" <will@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
Subject: Re: [PATCH v4 05/17] irq & spin_lock: Add counted interrupt disabling/enabling
Date: Wed, 5 Aug 2026 08:36:45 +0200 [thread overview]
Message-ID: <20260805063645.GO776954@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <anJUuzBcWRwyw6NJ@tardis.local>
On Tue, Aug 04, 2026 at 02:08:11PM -0700, Boqun Feng wrote:
> > > + /* Interrupts can happen here, but it's OK, see __irq_exit_rcu(). */
> > > +
> > > + if ((new_count & HARDIRQ_DISABLE_MASK) == HARDIRQ_DISABLE_OFFSET)
> > > + _local_interrupt_disable();
> > > +}
> >
> > Maximum nesting possible is 256 right? Whats is stopping here to do more than that?
>
> Yes. Currently similar as softirq, we don't detect the overflow.
>
> > Should there be a warn_on?
>
> A simple warn_on could be problematic because warn_on() itself may take
> an irq-disabling lock, and that may trigger another overflow on top of
> the existing overflow. It's a bit tricky to do a proper detection. But
> I'm open to ideas.
DEBUG_PREEMPT's preempt_count_add() does:
DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >= PREEMPT_MASK - 10);
next prev parent reply other threads:[~2026-08-05 6:36 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-04 16:14 [PATCH v4 00/17] Refcounted interrupt disable and SpinLockIrq for Rust Boqun Feng
2026-08-04 16:14 ` [PATCH v4 01/17] preempt: Track NMI nesting to separate per-CPU counter Boqun Feng
2026-08-04 16:14 ` [PATCH v4 02/17] preempt: Introduce HARDIRQ_DISABLE_BITS Boqun Feng
2026-08-05 6:31 ` Peter Zijlstra
2026-08-05 6:59 ` Boqun Feng
2026-08-04 16:14 ` [PATCH v4 03/17] preempt: Introduce __preempt_count_{sub,add}_return() Boqun Feng
2026-08-04 16:14 ` [PATCH v4 04/17] openrisc: Include <linux/cpumask.h> in smp.h Boqun Feng
2026-08-04 16:14 ` [PATCH v4 05/17] irq & spin_lock: Add counted interrupt disabling/enabling Boqun Feng
2026-08-04 18:20 ` Boqun Feng
2026-08-04 18:26 ` [PATCH v4.1 " Boqun Feng
2026-08-04 20:51 ` [PATCH v4 " Shrikanth Hegde
2026-08-04 21:08 ` Boqun Feng
2026-08-05 6:36 ` Peter Zijlstra [this message]
2026-08-05 7:07 ` Boqun Feng
2026-08-05 7:09 ` Shrikanth Hegde
2026-08-05 7:19 ` Boqun Feng
2026-08-05 13:53 ` Boqun Feng
2026-08-05 14:10 ` Shrikanth Hegde
2026-08-05 14:20 ` Boqun Feng
2026-08-05 14:56 ` Shrikanth Hegde
2026-08-05 15:11 ` Boqun Feng
2026-08-05 16:53 ` Shrikanth Hegde
2026-08-05 17:38 ` Boqun Feng
2026-08-05 18:07 ` Boqun Feng
2026-08-04 16:14 ` [PATCH v4 06/17] irq: Add KUnit test for refcounted interrupt enable/disable Boqun Feng
2026-08-04 16:14 ` [PATCH v4 07/17] locking: Switch to _irq_{disable,enable}() variants in cleanup guards Boqun Feng
2026-08-04 16:14 ` [PATCH v4 08/17] sched: Remove the unused preempt_offset parameter of __cant_sleep() Boqun Feng
2026-08-04 16:14 ` [PATCH v4 09/17] sched: Avoid signed comparison of preempt_count() in __cant_migrate() Boqun Feng
2026-08-04 16:14 ` [PATCH v4 10/17] preempt: Introduce HAS_SEPARATE_PREEMPT_RESCHED_BITS Boqun Feng
2026-08-04 20:11 ` Shrikanth Hegde
2026-08-05 6:54 ` Boqun Feng
2026-08-05 7:15 ` Shrikanth Hegde
2026-08-05 7:27 ` Boqun Feng
2026-08-06 0:58 ` Boqun Feng
2026-08-04 21:09 ` Shrikanth Hegde
2026-08-04 23:14 ` Boqun Feng
2026-08-04 16:14 ` [PATCH v4 11/17] arm64: sched/preempt: Enable HAS_SEPARATE_PREEMPT_RESCHED_BITS Boqun Feng
2026-08-04 16:14 ` [PATCH v4 12/17] s390/preempt: " Boqun Feng
2026-08-04 20:27 ` Shrikanth Hegde
2026-08-05 9:42 ` Peter Zijlstra
2026-08-05 12:37 ` Shrikanth Hegde
2026-08-04 16:14 ` [PATCH v4 13/17] rust: Introduce interrupt module Boqun Feng
2026-08-04 16:14 ` [PATCH v4 14/17] rust: helper: Add spin_{un,}lock_irq_{enable,disable}() helpers Boqun Feng
2026-08-04 16:14 ` [PATCH v4 15/17] rust: sync: Use super::* in spinlock.rs Boqun Feng
2026-08-04 16:14 ` [PATCH v4 16/17] rust: sync: Add SpinLockIrq Boqun Feng
2026-08-04 16:14 ` [PATCH v4 17/17] rust: sync: Introduce SpinLockIrq::lock_with() and friends Boqun Feng
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